Detroit Tigers (36-28) at Minnesota Twins (29-34)
Time/Place: 8:10 p.m., Target Field
SB Nation blog: Twinkie Town
Diamond was strangely mortal the last time he faced the Tigers, allowing three runs on nine hits in 5 2/3 innings. While he hasn't pitched very well overall this season, he has given the Tigers fits throughout his career. In two starts against Detroit this season, he is 1-0 with a 3.86 ERA. Take away those two outings, however, and Diamond's season ERA balloons to 5.51. His 4.30 FIP and 4.41 xFIP indicate that he may be getting a tad bit unlucky -- and a .350 BABIP agrees -- but that will happen when you're pitching in front of the defense ranked dead last in all of baseball in defensive efficiency.
For someone like Diamond, who is the current poster child of the Twins' pitch-to-contact philosophy, that's a problem. His command continues to be excellent -- he only walks 1.93 batters per nine innings -- and his line drive rate is nearly 3% lower than last season. Opposing hitters are reaching base at a .318 clip on ground balls this year, a fairly high rate once you consider Diamond's 49.1% ground ball percentage.
Looking deeper, the issue seems to be in Diamond's secondary pitches. He is still spotting his fastball fairly well, and while opposing hitters have a .311 average on that pitch, a lot of that success seems luck-driven. His ground ball rate on the fastball jumps to nearly 52%, yet hitters still have a .336 BABIP when they put that pitch into play. His changeup currently ranks as his worst pitch, at -4.16 runs per changeup thrown. However, he only throws it 11.4% of the time, and hasn't thrown it to a lefty all season long.
The curveball, on the other hand, has been ugly.
This chart shows opponents' batting average on Diamond's curveball based on location, and it's clear that he's hanging way too many of them. Opposing hitters have an ISO (isolated power) of .276 off the curveball this year. By comparison, Miguel Cabrera's 2013 ISO is .280. Scott Diamond's curveball is turning every hitter into Miguel Cabrera. Let that one sink in. It gets even worse when you consider that left-handed hitters have an ISO of .350 off the curveball this season. It's a big reason why lefties are hitting .356/.387/.525 off Diamond in 2013.
Obligatory Porcello stats update: since his start in Los Angeles, Rick has been rollin' his way to a 3-1 record, 3.24 ERA, 2.84 FIP, and 1.02 WHIP. The most impressive part? He's striking out 9.2 batters per nine innings during that stretch. A big reason for this jump in strikeout rate has been the improvement in his offspeed pitches. His changeup has been excellent all season, garnering a whiff rate of 16% compared to his previous career rate of 12%. Meanwhile, his curveball has gotten a lot better since leaving L.A. In his first four starts, opposing hitters had a whiff rate of 0.0% on the curve. After? That rate has jumped to 10%, and I'd wager that this rate would be even higher if PitchFX would stop labeling it as a slider.
Magic 8 ball: will Don Kelly play tonight?
Porcello's only rough starts since L.A. -- we should copyright that term at this rate -- was against this same Twins squad on May 23rd. Not surprisingly, it's also the only start he's had in this eight game stretch with fewer than five strikeouts. Given that the Twins rank in the top half of the American League in strikeout rate, I'm not sure if I'm worried about a repeat performance. Unfortunately, I'd also say the same about Diamond, who has a nice track record against this Tigers offense. If he can shake his home struggles -- he's 1-4 with a 6.41 ERA at Target Field this season -- the Tigers could be in for a long night.
Diamond returns to his Tiger-killing ways and the Twins start the weekend with a win.