Could David Peterson Be Chicago Cubs' Playoff Ace?

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It's never going to look as good as a good day for Kevin Gausman, Clay Holmes, Matthew Boyd or Shota Imanaga. The dominance of which those guys are capable is not quite within David Peterson's reach. He misses more bats than most ground-ball guys, but in the end, he's still a ground-ball guy. If you can be a ground-ball guy who also minimizes walks, you can still be an elite starter, but that's never been Peterson. He's capable of good, but not of great. He misses too few bats for that, given that he'll still put runners on base and isn't completely immune to hard contact.

The numbers don't lie, though. Over the last three starts, Peterson has been quite good. He fired six innings of one-run ball against the Reds Sunday, earning the Cubs a series win with his second straight quality start. He fanned seven and walked just one, after striking out another seven (and walking three) in six frames of equally strong work against the visitors from the Atlanta suburbs last week at Wrigley Field. Before that, he'd allowed just one run in a second straight start against the Brewers, at Uecker Field in Milwaukee. Craig Counsell was proactive with him that day, getting him out of the game after just 4 2/3 innings, but Peterson did his job: avoid damage and keep the team in the game.

That will be the remit of whoever pitches Game 1 of the Wild Card Series for the Cubs next Tuesday. be it at Wrigley or in San Diego, Philadelphia or the shadows of the highway northwest of Atlanta. As surprising as this state of affairs is, Peterson is building a case to be that guy. Consider this table showing the performances of Cubs hurlers with 30 or more innings since July 4:

Name	K%	BB%	K-BB%	BABIP	LOB%	ERA-	FIP-	xFIP-
Aaron Civale	23.3%	8.3%	15.0%	.250	83.8%	34	67	92
David Peterson	22.3%	10.6%	11.7%	.282	83.3%	70	96	86
Clay Holmes	16.3%	11.4%	4.9%	.240	65.6%	104	99	95
Shota Imanaga	25.1%	4.9%	20.2%	.283	91.5%	75	105	88
Kevin Gausman	26.6%	5.3%	21.3%	.297	70.7%	122	107	75
Matthew Boyd	16.1%	7.8%	8.3%	.246	74.8%	89	111	110
Javier Assad	17.9%	8.0%	9.9%	.268	91.5%	60	114	98
Colin Rea	17.5%	7.1%	10.4%	.246	78.9%	93	117	107

Now, there are some lies nestled in here. Don't fall too in love with Peterson's adjusted ERA (ERA-, where 100 is average and lower is better), lest you miss the fact that he's stranded five of every six runners who reaches base over this span. As you can see, Gausman is at the opposite end of the spectrum. Gausman has been better at striking out batters and at filling up the strike zone, as has Imanaga. Because only Imanaga has had the combination of guttiness and good luck to leave most of the runners who get on against him out there, though, only Imanaga has had the superficial sheen of a frontline starter.

Peterson is striking out a healthy number of hitters, which is more than Boyd or Holmes can say. However, he's also walking more batters than you'd like. The question is how willing you are to trust that Peterson can persistently outperform his FIP, by stranding runners (or eliminating them via the double play) and by keeping the ball in the park.

That last bit is the key, though. What separates Peterson from everyone else on this list? He avoids giving up home runs—at least when he's going well. He's only allowed nine homers since coming to the Cubs; seven in his last 13 starts; and four in his last nine. Because he keeps the ball on the ground, he can frustrate power hitters who depend on hitting it in the air to generate value. The rest of this starting rotation candidate pool can't say that.

If Gausman, Boyd and Imanaga come through their final starts looking healthy and pitching the way they each have of late, they're the most likely hurlers to be tabbed for starts in the Wild Card Series. In reality, though, Peterson might be as deserving of the chance as any of those three. That's not great news for the Cubs' starting staff. A World Series contender needs two starters who are clearly superior to Peterson, which is two more than the Cubs have. If they want to press deep into October, though, they might be well-advised to give the ball to a starter they acquired only in an emergency and have never really looked at as more than a back-end guy.