You can read Parts 1 and 2 of our State of the Astros (All-Star Break Edition) here and here.
Overall
Overall the Astros have had a decent set of arms, posting a 10.1 WAR so far this season. Their 3.79 ERA is 10th in baseball, right in line with the 3.71 FIP and 3.94 xFIP. They have benefited from the use of shifts and focus on defense with a .279 BABIP, tied for 3rd in baseball, and just three points behind the .276 Royals. Overall the 49.6% groundball rate is 3rd in baseball, as well. Solid.
Starters
For some reason, the pitching staff has been seen as a major source of weakness - and it shows how far the Astros have come that this pitching staff is far better than we've seen in recent years. Overall, Astros starting pitching has posted a 7.9 WAR (via FanGraphs) - good enough for 10th in all of baseball, and 4th in the American League. Most of this can be attributed to Dallas Keuchel, about whom we will talk later in this space. But it's worth noting that the 2013 Astros posted a 6.8 WAR for the entire season. The Astros K/9 rate sits at 7.16, 14th in MLB, while the 2.77 BB/9 is 20th. Their 70.3% LOB rate is 4th-worst in baseball, but the groundball rate of 50.4% is 3rd-best in baseball, behind the Dodgers and Pirates. The Astros' 4.02 ERA is 16th in baseball, showing they've been a little unlucky what with the 3.70 FIP and xFIP.
Dallas Keuchel
Arguing whether Dallas Keuchel is an ace is like arguing whether a hot dog is a sandwich, because if you're the best pitcher on a team's rotation, you're the ace. Just like when Brett Myers was the ace of the rotation back in It Doesn't Matter When. And because the answer to both is yes, because they are, that's why. Keuchel's 3.4 WAR is 5th among all starters, behind Max Scherzer (4.7), Chris Sale (4.1), Corey Kluber (3.9), Clayton Kershaw (3.7), and tied with Sonny Gray and Jake Arrieta. Keuchel is the best pitcher on a team of decent to good pitchers. Keuchel is posting career highs in K/9, BABIP, LOB%, GB%, ERA, FIP, and xFIP. He's already 2.7 WAR better than he was in 2014.
Keuchel hasn't had a start where he failed to get 18 outs, going at least 6IP since July 19, 2014, a span of 30 starts. He has record at least 21 outs in 12 of his 19 starts this season. Keuchel is a #1 starter. He's arbitration eligible in 2016 and won't be a free agent until 2019.
Collin McHugh
McHugh has not built on the successes of his surprising 2014. He has shown flashes of recapturing last season, but for the most part it has eluded him, in large part due to his .298 BABIP. This is a fairly normal BABIP, but it's almost 40 points higher than the .259 BABIP he posted in 2014. McHugh's ERA sits at an aesthetically pleasing 4.50, a scoach unluckier than his 4.00 FIP and 3.92 xFIP. Part of the issue is his new-found tendency to give up home runs (0.76/9 in 2014, 1.11/9 in 2015. His groundball rate has increased from 42.1% to 46.7%, they're just finding holes. His strikeouts are down from 9.1 per 9inn to 7.2 per 9inn.
After not giving up a home run in his first four starts, McHugh then gave up four solo homers on May 2, and has given up at least one home run in eight of his last 14, and gave up eight homers in six starts between May 27-June 18. One of the issues McHugh is facing is his sudden struggle with right-handed hitters. In 2014 McHugh held righties to a .190/.251/.305 line. So far in 2015, RHBs are hitting .287/.344/.461. And while we're dealing with a small-ish sample size, righties are hitting .308/.354/.500 at Minute Maid Park off McHugh.
Despite all of that, since McHugh gave up 8ER in 3IP against Seattle on June 13, he has thrown 34.1IP in five starts, with 26H/12ER, 29K:12BB and just two home runs allowed.
Lance McCullers Jr
McCullers has been The Troof. His 1.9 WAR in just 11 starts is fun because it's tied with Noah Syndergaard and Chris Heston for highest WAR among rookies. In fact, McCullers compares favorably to Syndergaard. McCullers has a higher K/9, lower HR/9, higher LOB%, better ERA. The only place McCullers is needing obvious improvement is his walk rate of 3.36 BB/9. That's too high. And part of it is because of McCullers' efficiency. He has electric stuff, but he's throwing too many pitches, having failed to record a 16th out in five of his 11 starts, and failing to get out of the 5th in three of those starts. He has thrown 1063 pitches to 262 batters in the Majors - an average of 4.06 pitches per batter and 16.5 pitches per inning.
The Astros are 4-7 when he starts, but have scored a total of 15 runs in those seven losses. McCullers is going to be on an innings watch, seeing as how he threw 104.2IP in 2013, 97IP in 2014, and has already thrown 93.1IP between Corpus and Houston. The Astros have already taken steps to limit his innings - from skipping starts to possibly sending him to the bullpen.
Scott Feldman
Vince Velasquez
Brett Oberholtzer
SP4/5 spots are up in the air. Feldman has been out since the end of May, and the 5th spot has had a variety of faces: Asher Wojciechowski, Dan Straily, Not Fausto Carmona, Brett Oberholtzer. So you can see why the Astros are in search of another arm to push some of these names down a little bit. McCullers isn't going anywhere, so if you consider the Astros as having four arms (Keuchel, McHugh, McCullers, Feldman), then Not Fausto, Oberholtzer, Velasquez, Wojciechowski, Straily, and Deduno have combined to make 33 starts.
Feldman's numbers are inflated by two starts: April 13 vs. Oakland, and May 5 vs. Texas. In those two starts, Feldman threw 8IP, 19H/13ER, 2K:2BB. In the other eight starts he has thrown 52IP, 49H/19ER, 35K:12BB. He's not going to strike out All The Batters, but that's not why the Astros signed him. His 5.6 K/9 rate is exactly right in line with his career K/9 rate. Feldman's 4.80 ERA is belied by a 4.06 FIP and a 3.61 xFIP. He's been unlucky - suffering from a .318 BABIP, and his GB% had risen from 2014's 46.9% to 49.7% after ten starts. Feldman gave up five home runs in his first three starts, and two in his last eight starts. If he can stay in the 4.00-4.50 ERA range, I think the Astros will take that towards the back of the rotation.
Velasquez made six starts in his first stint with the Astros this season, for 32IP, with 28H/14ER, 31K:14BB. His 3.94 ERA is in line with his 3.67 FIP, so it's not smoke and mirrors. But like McCullers, Velasquez will need to work on his efficiency. His 32IP come from six starts, but he record 19 outs in each of his last three starts - meaning he averaged 7.28 pitches per out in his first three starts, and 4.92 pitches per out in his last three starts. And like McCullers, the Astros will be keeping an eye on his innings total. He has thrown 58.1IP between Corpus and Houston in 2015, and threw 77.2IP in in 2014, including 13.2IP in the Arizona Fall League. In 2013 Velasquez threw 124.2IP in his second year removed from Tommy John Surgery.
Brett Oberholtzer has been an absolute mixed bag in 2015. He was 5-13 in 2014 with a 4.39 ERA, but a 3.56 FIP, so the Astros were hoping he could get a little closer to what the numbers expected out of him. And he finished strong-ish in 2014, throwing allowing 43ER in 92.2IP with 10 quality starts in 15 after coming back from Triple-A in June 2014. Then 2015 happened and he started the season with blister issues. His only Disaster was that game against the Yankees where he allowed a 1st inning grand slam, another homer, and then apparently attempted to throw at A-Rod, which earned him an ejection and a demotion in what has been the worst post-game celebration of the year. Subtracting that horrible start, Oberholtzer has thrown 37IP, 40H/13ER, 26K:14BB.
Point is, the Astros just don't know what they're getting for the rest of the season from a handful of pitchers. They'll treat McCullers and Velasquez carefully - and rightfully so - and not ride them like they're Max Scherzer. Oberholtzer is a big ol' question mark, for some reason. So basically the rotation options are Keuchel, Dr. McHugh and Mr. Hyde, two guys who were in Double-A two months ago, a 32-year old coming off knee surgery, and Brett Mixed Bag Oberholtzer. Yeah, the Astros could use another starting pitcher. But do they need Johnny Cueto for two months?