How Good is the Cubs' Rotation, After Its Winter Reinforcements?

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Image courtesy of © Jesse Johnson-Imagn Images

It's an awkward time of year to review (or even preview) a starting rotation. Teams often go into camp with up to nine potential starters and (if they're very lucky) a couple of intriguing prospects. At least one projected member of the 26-man roster usually hits the injured list before Opening Day. There's still the chance for trades and signings, but what we see right now is the Cubs' Plan A for the rotation.

The pitching injury rates of the current era necessitate serious depth. Last season was a good lesson for the Cubs on that score, as three members of their Opening Day rotation—Justin Steele, Shota Imanaga and Jameson Taillon—missed significant time due to injuries. Matthew Boyd didn't miss time, but that was the first time in over half a decade that he'd stayed healthy all year; he's unlikely to do so again. Hence, we see the Cubs remaining interested in additions to their starting depth chart. For now, though, let's taxonomize the guys who are coming to camp as rotation candidates.

Measuring Aces vs. Mid-Rotation Contenders
In the top tier of starting pitching, you don't want to make any longwinded excuses for anyone. You want the statistics to leap off the page and command confidence. Ideally, you want at least one such stud at the front of a rotation. Do the Cubs have one? Let's define an ace arm in very simple terms.

An ace arm should rank in the top 40 in the league in terms of long-term fundamentals. You don't want the guy to be too dependent on finesse and luck against the world's best hitters. We'll use two stats for fundamentals: Expected ERA (xERA), and Pitching+, via Fangraphs, the latter of which combines Stuff+ and Location+ modeling. A player with fundamentals below these expectations (even one who manages to get results) is showing a red flag: Those ace-caliber results may be inconsistent going forward. Still, there are plenty of dudes who have a complex approach to hacking the fundamentals, and the Cubs specialize in finding those guys.

More importantly, perhaps, an ace will rank in the top 25 in basic results. We'll combine three measures to rank pitchers on that front: Earned Run Average (ERA), Home runs per nine innings (HR/9), and walks per nine innings (BB/9). One's ERA is the natural statistic for how reliable a player is, but it can sometimes overlook an elite player because of a few bad outings, or poor defensive support. Homer rate is less important during the regular season, except in extreme cases, but it becomes very important for assessing a player's ability to face elite slugging lineups in the postseason. Meanwhile, limiting walks is essential for amassing quality starts during the season but has a bit less impact against elite contact hitters in postseason.

I computed total indices as an average of all five statistics, but with ERA weighted three times as heavily as the other two. After all, we want to emphasize run prevention in this portion. We'll also give a pitcher some extra credit if they play good defense, including controlling the running game well.

For a World Series hopeful like the Cubs, you'd like to see the top 5 starting options to rank in the top 75 in both xERA and ERA (out of 127 players in the year 2025 who had 100 or more innings), and all of them, obviously, should be as highly ranked as possible.

Without further ado, let's evaluate the leading three options for ace quality, based on their 2025 statistics. (Note, in the case of Boyd, adding in 2024 would inflate his overall results into clearer ace territory, but it was a small sample).

The Top Trio: Cade Horton, Matthew Boyd, and Edward Cabrera

Horton

• ERA: 12th (2.67)
• HR/9: 18th (0.76)
• BB/9: 51st (2.52)
• xERA: 44th (3.88) 
• Pitching+: 70th (97)

TOTAL WEIGHTED RANK, 2025: 31
An elite pitcher rarely peaks in their rookie year. Ideally, a hurler loses some "major-league jitters" their sophomore season. Horton had ace-like numbers in ERA and HR/9 in his debut. He was appropriately showered with affection during Rookie of the Year voting. His best results came during the second half of the season ,when you most need it. His overall stuff and expected ERA should both be better this year, as we have seen him do better in minor-league performances with clean bill of health. If you're an optimist, you see an ace in the making. I expect top-40 fundamentals and top-25 results in 2026. It's worth remembering, though, that "sophomore slumps" are as real as those jitters we mentioned earlier.

Boyd

• ERA: 29th (3.21)
• HR/9: 29th (0.95) 
• BB/9: 23rd (2.10) 
• xERA: 33rd (3.75)
• Pitching+: 76th (96)

TOTAL WEIGHTED RANK, 2025, including good fielding bonus: 25
Boyd is famous for his nice guy attitude and leadership on the mound. Here's a mid-velocity lefty with very good breaking pitches, who really remade himself last year. I believe his career year in 2025 has some chance to be repeated, but his stuff has hit a hard ceiling. His Gold Glove-level defense makes him a borderline ace; he kept runners in check as well as anyone in baseball last year. His results are quite fringy for an Ace, without factoring in defense. However, as a lefty with 5 decent or good pitches, we can give him quite a bit of leeway on velocity, too. 

Cabrera

• ERA: 42nd (3.53)
• HR/9: 51st (1.11)
• BB/9: 80th (3.14)
• xERA: 56th (4.05)
• Pitching+: 21st (107)

TOTAL WEIGHTED RANK, 2025: 47
Cabrera is virtually the opposite of the typical Cubs starter: a guy whose raw ingredients hint at an ace, but who has yet to put it all together for a full season. His numbers profile as classic third option, but with good enough momentum to be a trusted No. 2. The bad news is that he drags the Cubs down from an elite walk rate; the good news is his results should improve in the Friendly Confines, and with the pitcher-friendly Cubs defense behind him. The even better news is that he's young and has showed steady improvement three seasons in a row. He had a four-month stretch last year wherein he was in the top 5 in ERA.

The 4-6 Rotation Arms: Justin Steele, Shota Imanaga, and Jameson Taillon
Breaking down the less starrish arms can lead to many arguments. You'll see cases of very high WAR and xERA paired with a bad ERA (Ben Brown, 2025), or a consistently impactful starter with a deceptively low WAR and stellar ERA (Jameson Taillon's 2024). Overall, the Cubs can be proud of their fourth through sixth guys; they're better than the back half of many rotations. The best of the bunch, Steele, certainly belonged to the first tier of the team's starters before his injury last year, but that very thing now makes it harder to gauge what the team will get from him and when. We'll judge him based on his 2024 stats, since he essentially lost 2025.

Steele

• ERA: 17th (3.07)
• HR/9: 19th (0.80)
• BB/9: 52nd (2.47)
• xERA: 7th (2.81)
• Pitching+: 52nd (102)

TOTAL WEIGHTED RANK, 2024: 26
Steele's 2024 self was as good as the team can reasonably hope for Horton, Boyd or Cabrera to be. However, two problems restrict his ranking in 2026. First, pitchers rarely play their best ball when they come back midseason from injury, especially in terms of fundamentals (Pitching+). Second, his results were a just below the desirable cutoff of top 40 in Pitching+, and thus, he's likely to face regression. He succeeded so much with precision before shredding his elbow that it's hard to expect him to be as good afterward. Between these two factors, we must expect Steele to have a shortened and diminished 2026. If he can reclaim health, he'll still be atop the rotation in 2027. 

Imanaga

• ERA: 20th (3.28)
• HR/9: 108th (1.64)
• BB/9: 4th (1.53)
• xERA: 28th (3.66)
• Pitching+: 39th (104)

TOTAL WEIGHTED RANK, 2024 AND 2025: 34
Here, by the way, I've used his last two seasons' numbers taken together. I wish we could just roll with his 2024 stats, because he flashed ace-level results in his first major-league year. It's safer, though, to assume that he'll be somewhere between the stud he was that year and the suspect he was down the stretch of 2025. His velocity really became a problem last season, as he lost over 1 mph while navigating a stubborn hamstring strain. Still, the upside is real. We've seen it relatively recently, and he's a tenacious and creative competitor.

Taillon

• ERA: 28th (3.45) 
• HR/9: 83rd (1.37)
• BB/9: 12th (1.83)
• xERA: 46th (3.95)
• Pitching+: 60th (100)

TOTAL WEIGHTED RANK, 2024 AND 2025: 41
We'll look at each of the last two seasons again here, to accentuate the reliability of the team's veteran workhorse. Taillon has put together two very impressive seasons, with a near-ace ERA and an elite walk rate that is confidence-inspiring. Still, his low strikeout rate hurts his xERA. In addition, those darn homers keep him out of postseason primacy. The only good news in that category is that he had a career-worst HR/9 year in 2025 and regression should be expected. Taillon has the exact profile of a season-long innings eater who wins many games with ruthless efficiency. He's definitely worth his $18-million salary, but he won't carry you in October like $30-million arms do.  

The Rest of the 40-Man Starters

Colin Rea, Ben Brown, and Javier Assad: Better Than You Think
Let's look at the rest of the important arms quickly. Colin Rea and Ben Brown finished last season with xERAs of 4.52 (85th) and 4.53 (86th), respectively. This means each team has, on average, three better pitchers capable of giving 100+ innings. When we look closer, it gets better. In BB/9, Rea was 50th (2.49), and Brown was 55th (2.71). Rea was tied for 52nd in HR/9 (1.13), whereas Brown can brag about his Pitching+'s 70th rank (97) being a floor, not a ceiling.

In the case of Assad, you've got a guy who is much like Rea in junk pitching style, but somehow always outperforms Rea's (and his own) fundamentals. In terms of players with at least 250 innings pitched from 2023-2025 (134 results), Assad's ERA is shockingly good, at 29th-best (3.47). Adding to that, he boasts a HR/9 (1.10) that ranks 52nd, despite a sad xERA of 4.98 (117th) and equally bad BB/9 of 3.56 (117th). His horrendous Pitching+ scrapes the bottom of qualified players, and explains why he rarely strikes anyone out. This huge gap between actual and expected performance is why most analysts believe Assad will never again repeat his best two seasons. His best role on a good team is in long relief, although a non-contending team would immediately stick him into the back of the rotation. 

Caveats
Clearly there's no exact science for projecting results from prior history. Pitching can be rather volatile across a season, let alone multiple seasons. The simplest evaluation is the most recent healthy year, though in some cases, two years is more appropriate.

Comparisons: Who Potentially Has Three or Four Aces?

Instead of thoroughly evaluating all 30 ballclubs, let's just compare six of the scariest rotations on highly complete contending squads: the Dodgers, Braves, TIgers Mariners, Phillies, and Red Sox. The point here is merely to illustrate how good the Cubs really are, rather than predict the relative quality of these teams. 

The Dodgers Stand Alone
Los Angeles has an embarrassment of riches, of course. Yoshinobu Yamamoto, Shohei Ohtani, Tyler Glasnow and Blake Snell stand clearly above the Cubs' top four, although not by as much as you may think. It's hard to make statistical comparisons, because three of the four didn't have 100+ innings in 2025 or 2024. It will be interesting to see if they actually meet their lofty expectations. Of course, it doesn't end there. Roki Sasaki and River Ryan could blossom into deadly weapons this year. 

Four Top-Quality Performers, When Healthy: The Mariners, Tigers and Braves
Seattle still has its deadly ace trio of Bryan Woo, Logan Gilbert, and George Kirby. Luis Castillo, who has some fringe ace stats at his best, is comparable to Cabrera in ERA and xERA. However, their next three guys can't compete with the Cubs' fifth through seventh options (Imanaga, Taillon, and Rea). 

Detroit can go man-for-man with Seattle, after signing Framber Valdez and Justin Verlander to complement their previous top duo of Tarik Skubal and Jack Flaherty. Skubal is, without controversy, the best pitcher in baseball. Valdez is an ace in his own right, and Verlander and Flaherty are solid mid-rotation pieces. The team won't have Reese Olson to round out their staff this year, as Olson is set to undergo season-killing surgery, but they have a handful of other young arms and former No. 1 pick Casey Mize to brace them against the risk of an injury to Verlander.

Until camp opened, it looked like Atlanta would fit into this tier, too, although more tenuously. Chris Sale remains dominant at times, but is starting to age. Spencer Strider returned from Tommy John surgery, but wasn't his best self. Reynaldo López missed last season with shoulder trouble, and now Spencer Schwellenbach will spend at least the first two months of the year on the IL, too. The upside is very high for the Braves, but the downside is coming after them.

Two Studs, One Fringe Ace: The Red Sox and Phillies
Philadelphia's Christopher Sánchez, Zack Wheeler, and Jesús Luzardo (fringe) are good enough to top Horton, Boyd, and Cabrera, but Wheeler is coming off thoracic outlet syndrome and won't be ready to start the season. Similarly, Boston's Garrett Crochet, Ranger Suárez, and Sonny Gray (fringe) trio can strike fear in batters' hearts. Boston has better depth; Philadelphia has better upside. Neither is clearly superior to the Cubs, though.

Conclusion

Though other teams have truer aces, the Cubs blend depth and upside as well as almost anyone. They'll have to prove that they can hold up, and Cabrera and Horton have to take the next step after their quasi-breakouts in 2025, but this is an October-ready starting rotation. Unless and until they run into the Dodgers, they can hang with anyone.

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