Is Johnny Cueto the ace the Reds need?

Last night, Johnny Cueto pitched seven innings of shut out baseball in San Francisco, striking out eight while walking two and scattering four hits in what FanGraphs called "far and away Cueto’s best start of the year".  It was the third time in his young season that he blanked the competition, and the fourth time he pitched at least seven innings.  His season started a month late, but in the month he's been in the Reds' rotation he's been an anchor, going deep into games, saving the overworked bullpen arms, and giving the team a chance to win.  He's sporting a sparkling 1.93 ERA after last night's outing.  In this, his age 25 season, has he made the leap from good pitcher to legitimate staff ace?

In a word: hopefully.  He's thrown fewer than 50 innings so far, so we shouldn't be rushing to crown him just yet.  But there are some interesting patterns emerging that are worth examining. 

First off, we should look back at what he's done in the past few years to see what he's doing differently.  Cueto's peripheral stats (K/9, BB/9, and HR/9) have decreased every season since his rookie year when he struck out an impressive 8.2 batters per 9 while walking a decent 3.5 per 9.  His bugaboo was (and has been) his penchant for giving up the gopher ball, as he gave up 1.5 HRs/9 that season.  That's not quite as many balls as Bronson has served up this season, but it's not good.  In subsequent years, he's seen each of those numbers drop, as he's apparently pitched more to contact and been able to keep the ball down more.  Last year those numbers were down to 6.7 K/9, 2.7 BB/9, and 0.9 HR/9.  It's been a steady maturation process, but one limited by his decreased ability to rack up the Ks and his vulnerability to the long ball.  Aces can get away with giving up the occasional home run ball as long as they are striking out tons of hitters, but the ceiling is low for guys who give up the dingers without the punch outs.

But this year is a bit different.  His BB/9 (2.7) and K/9 (6.0) are still on par with last year, but he's nearly halved his already-above-average 3.64 ERA from last year.  One major reason for this is a dramatic increase in ground balls.  Coming into this year, he'd induced ground balls around 40% of the time.  So far this season, he's getting them 54.5% of the time.  This has had a most dramatic impact in two key areas for Cueto: that old bugaboo of a HR rate and his GIDP rate.  His HR rate is down this season to a very respectable 0.58 from a career rate around 1.25 and his GIDP is up to almost 1.0 from a career rate of 0.59.  Turning a few of those three-run-homers into inning-ending double-plays is a sure-fire recipe for victory chili.  This is a most encouraging (and delicious) development indeed.

As a counter though, his BABIP is down to a probably-unsustainable .230.  Just how unsustainable that is is up for debate, though.  It seems hitters are making more contact on him this year, but much weaker contact.  His contact% is up to a career-high 85% (80% last year) but his line drive rate is down 3.7%, his fly ball rate is down fully 9%, and his ground ball rate is up 12.8%.  That probably doesn't mean a 60 point drop in BABIP, but it does mark a distinct change in the way Cueto is pitching and getting results.

So has he graduated to acedom?  Like I said above, I'd like to see him keep this up all season before I make such a judgement.  But the numbers look sustainable, which is a very encouraging sign.  He could just be on a hot streak, or he could be seeing the fruits of hard work and maturation.  The way this rotation is looking so far this year, we have to really hope it's the latter.  The Reds' playoff hopes could depend on it.

All stats from B-Ref and FanGraphs