The Oakland A’s rotation has been pretty good, despite some adversity

Not a lot has gone right for the last-place Oakland A’s this year. The lineup is only good at hitting solo homers, the defense is arguably the worst in the sport, and the bullpen is fine except for when it really matters. But at 17-23, not everything has gone wrong, and the brightest spot so far has been the starting rotation.

There are plenty of reasons why the rotation should be a weakness. Four starters have gone on the DL since February, and of the healthy ones, top prospect Jharel Cotton struggled enough to be sent back down to the minors. And yet, despite all that, the group has held serve admirably, patching every hole as it comes up with only one true emergency spot start so far. Here are some big-picture numbers:

• 12th in ERA (4.23)
• 5th in FIP (3.93)
• T-9th in fWAR (3.1)

A’s starters are in the top half of MLB in preventing runs, and remember they’re pitching in front of the worst defense in baseball. They’re also backed up by a bullpen that’s the worst in the sport at stranding inherited runners (41% score), so they’re being tagged with a few extra runs that way too. The starters’ overall strand rate for all their baserunners (LOB%) is dead last (65.2%), two percentage points below the next-worst and more than seven below league average.

Given all that, Oakland’s rotation has actually been even better than their decent ERA suggests. When you boil it down to the things the pitchers can control, like strikeouts, walks, and homers, they’ve been one of the best in the business — hence their excellent ranking in FIP (Fielding-Independent Pitching).

• 18th in K% (19.4%) (7.43 K/9)
• 19th in BB% (8.8%) (3.36 BB/9)
• 1st in HR/9 (0.86) (as in, lowest)

Context: 2017 MLB average for starters is 20.3% for Ks and 8.4% for BB.

As you can see, the A’s are only actually excelling in one of those areas: preventing home runs. Their lead is substantial, too, as the difference between them and 29th is more than the difference between 29th and 19th. MLB average is 1.27 HR/9.

Is that homer-suppression real, or a small-sample fluke? Normally I’d heavily caution the latter, but I’ll offer some hope in this case.

Of these three areas (K, BB, HR), homers are the one the pitcher has the least control over, but that doesn’t mean they have no control over it. If you let batters hit flyballs then some of them will eventually go over the fence, but you can get around that by simply not letting them hit it in the air.

That’s what Oakland’s starters are doing, at 4th in MLB in groundball rate (49.4%) — and they’re even more extreme now without Cotton, who was the only one of the group under the high-40s (37.7%). When you look at their homers in relation to the number of flyballs they allow, they don’t even quite lead the league — their 9.7% HR/FB rate is second to Detroit.

And even better, they’re in the top 10 in terms of inducing weak contact and avoiding hard contact (yes there is a third classification, medium; that’s not a redundancy!). And they do still pitch in the friendly Coliseum half the time, an advantage that isn’t going to go away.

Point being, their low dinger rate is excellent, but not so ridiculous that it’s too good to be true. It’ll probably regress a little bit over a full season, and perhaps the whole thing is a mirage and they’re just getting lucky during an especially cool California summer, but for now it’s safe to say the A’s rotation is good at limiting home runs.

One more important part of a starter’s profile: endurance.

• 16th in innings (219⅓)
• 19th in innings/game (5.48)
• Bulleted lists should really have a third item

(Yikes, I couldn’t finish the list on endurance.) The only item on that list you really need is the rate stat, which shows A’s starters aren’t quite carrying their weight in terms of quantity. They’re pitching well when on the mound, but not staying out there quite long enough — especially given the bullpen isn’t a strength right now.

I’m not too worried about this shortcoming at the moment, though. The rotation is various shades of young and inexperienced (age range: 25-28), and they’re sometimes being eased into shorter outings as they return from their frequent injuries. They’ve also tossed 19 Quality Starts, at a rate of 48% of the time, both of which are just above MLB average. This is one thing that may improve on its own over time.

Overall, the A’s rotation has been good-not-great. The secret to the success they’ve enjoyed has been extreme home run suppression, which might not last at its current peak level but is probably a real skill this group possesses to some extent. Their K/BB rate is unspectacular, but they have the valid excuse of successfully pitching to weak groundball contact, though that’s a risky strategy in front of such a porous defense.

The next biggest question facing this rotation is how long it will last in its current form. Andrew Triggs is the “ace” in terms of having the best numbers, but how many innings can he throw this year after spending his career as a reliever? Will Sonny Gray, Sean Manaea, and Kendall Graveman all stay healthy after early DL stints? Will the Good Jesse Hahn keep showing up, or will Cotton catch up with him again? Beyond these top six guys, will the supply of new prospects meet the demand, or will they be turning to the next Cesar Valdez, and if so how soon?

The A’s rotation is off to a good start despite their share of adversity, but they still have a lot to prove. So it goes in the world of young pitchers.

Individual Stats

A quick look at how each pitcher fares in the categories we just discussed. Cotton is included as well since he’s been a significant contributor.

Context: 2017 MLB average for starters is 20.3% for Ks, 8.4% for BB, and 44.4% for grounders.

A few notes:

• Regarding Manaea’s low IP/G, remember that on one occasion he was pulled after two innings due to injury. If you remove that game, he’s right in line with the others (5.47).
• Manaea’s grounder rate puts him 7th among MLB starters.
• It’s not entirely clear due to sample size differences, but Triggs and Hahn are the leaders in terms of HR prevention (way more innings than Manaea and Sonny).
• None of them have a K/BB ratio above 3.00.