Miguel Amaya Returns to Cubs Lineup: Can He Maintain Team's Extraordinary Control of Baserunners?

[Matthew Trueblood]

Image courtesy of © Rick Scuteri-Imagn Images

Reese McGuire survived the reinstatement of Miguel Amaya from the injured list this week. Instead of cutting McGuire, the Cubs designated Jon Berti for assignment. For now, at least, the team will carry three catchers in their 13-man pool of position players. Barring something unforeseen that forces them to take a different tack, the hope seems to be that they can keep all three around until September. At that point, they'll be able to add another position player to their roster, while still retaining the three backstops.

If that seems like a lot of temporary roster ossification in the name of holding onto McGuire (who's batting .235/.250/.459), it is, but there's a reason for that. With Amaya on the shelf, McGuire and Kelly formed not only a respectable offensive tandem at the game's most defense-first position (other than pitcher), but one of the most formidable impediments to opponents advancing on the bases of any team in the league. They haven't merely been good; they've been elite.

Baseball Reference offers a table showing the number of Stolen Base Opportunities (SBO) against a catcher, defined as any plate appearance in which a runner was on first or second with an empty base in front of them. We might reasonably call that stat, instead, Advancement Opportunities, because there are other ways (balks, wild pitches, passed balls, and so on) than steals to move up, but we can leave the label as it is. We're going to use it only as a rough-hewn denominator.

The same page also offers totals of Runner Bases Added (RBA). This is the total number of bases taken against a catcher via steal, passed ball or wild pitch. Finally, there's Runner Kills (RK), which is the number of runners the catcher threw out on the bases. These stats are also tabulated at the team level.

To give a sense of the context of these numbers, the median teams in the league have allowed 159 (the Rangers) and 153 (the Guardians) Runner Bases Added. The Marlins are worst in the league; they've allowed runners to take 223 bases against them. The Royals are the best, at 104—although that might change, because they traded defensive whiz Freddy Fermin to San Diego last month. The median teams (the Athletics and Giants) have 32 Runner Kills, with the White Sox leading the way with 45 and the Angels bringing up the rear at 19.

The Cubs are, for the season, second-best in baseball at preventing Runner Bases Added, at 113. They're great at stifling the running game, but it's not just deterring and cutting down basestealers. The team's catchers have also been superb at blocking balls in the dirt and shortening secondary leads for opposing runners. Only the Royals have them beat in that department. Chicago is just fifth in Runner Kills, at 41, but the four teams in front of them have allowed an average of 170.5 Runner Bases Added. One sure way to rack up Runner Kills is to be somewhat bad at stopping the running game; teams start getting more aggressive and the number of outs rises, but not as fast as the number of advancements.

A good way to quickly estimate the efficiency of a catching corps (and their batterymates, who also play a major role, of course) in containing runners, then, is to find the number of Runner Kills per Base Added. The Cubs lead the league in that metric, pretty easily. They're at 0.36; the closest team to them is the Phillies, at 0.30.

Let's talk about the individuals involved, though, because their specialties are different, and Amaya's reintroduction is an interesting wrinkle. There are 99 catchers who have been behind the plate for at least 100 Stolen Base Opportunities this year, including all three Cubs. If we use that threshold to eliminate guys with tiny samples that make their numbers meaningless, it's easy to derive rate stats for RBA and RK. Simply put: what percentage of SBOs yield an advancement, whether it be via steal or something else? As it turns out, the average in that area is 10%. What percentage of SBOs result in a runner being thrown out, via back-pick, caught stealing, or a thwarted attempt to advance on an errant pitch? That figure is about 2%. Those are your baselines.

Of those 99 catchers, only Fermin, Hayden Senger of the Mets, and Korey Lee of the White Sox have held runners to a lower Advance Rate than Kelly—and then only by tiny margins. Kelly roughly halves the rate at which runners advance, relative to the average catcher; his Advance Rate is 5%. Both Amaya (8%) and McGuire (9%) are also better than average, but this is Kelly's superpower. The nine wild pitches and three passed balls in his huge volume of time behind the plate are extraordinarily low numbers; that's why he's also rated as an above-average blocker in Statcast's Catcher Blocking Runs metric.

In that same pool, though, no other catcher in baseball has a higher Kill Rate than McGuire's 5%. Kelly and Amaya are each about average in that regard, at 2%, but (whether purely because of circumstance, or because his sheer arm strength scares them less, or because he has more balls get just a bit away from him) runners do test McGuire—and he makes them pay. His 14 RK have come in 301 SBO. The other four catchers with 14 RK have gotten there in an average of 738 SBO.

McGuire's framing has been solid, too. His role with the pitching staff is important, just as Kelly's and Amaya's are. Holding onto all three of these guys makes sense, because slowing the trip around the bases as well as any other team in the league has helped the Cubs keep opponents' run totals down throughout a long season in which they've battled several pitching injuries and a month or so in which their offense has left little margin for error.

Bringing back Amaya could partially alleviate that lack of scoring. However, Kelly and McGuire were already doing an unimpeachable job of helping the team stay afloat even while not scoring much—and while Amaya is good at the same things, he's not quite on the level of the two teammates he's rejoining in the catching rotation.

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