I can't say I blame Luke Gregerson. The veteran reliever signed with the Houston Astros as a free agent for 2015, got a chance to be a full-time closer for the first time in his career and saved 31 games in 36 opportunities, posting a 3.10 ERA with 59 strikeouts and just eight unintentional walks in 60 innings.
Yes, the sinker/slider specialist doesn't throw hard and, yes, he was part of the eighth-inning meltdown in Game 4 of the division series when the Astros blew a four-run lead, although it was already 6-6 with runners on second and third when he entered. Gregerson walked light-hitting Drew Butera and then gave up an RBI groundout. Maybe if he'd entered earlier the Astros would have kept the lead, clinched the series and who knows what would have happened after that.
A veteran usually has to lose his job, not have it taken away, especially if he has come off a solid season. In this case, the Astros went out and acquired hard-throwing Ken Giles from the Phillies and he'll presumably take over as closer. Gregerson doesn't appear too congenial about the idea. "How do you think I did last year? I don't see any reasons things should change," he told the Houston Chronicle. "I don't see any reason why I should lose my job because of it."
Should he? Let's dig a little deeper into Gregerson's 2015 season.
Among 28 relievers with at least 20 saves, he ranked 23rd in save percentage at 86.1 percent. So while 31 of 36 sounds pretty good, it's below average for a closer.
Among those 28 closers, his average leverage index was 16th, according to Baseball-Reference.com. Leverage index factors in the score and situation of the game when the reliever enters. Of course, like most modern closers, Gregerson almost always entered to start the ninth inning. But he didn't face an unusually high number of one-run leads or anything.
Again comparing Gregerson just to those 28 closers, he ranked 10th in wOBA allowed and 21st in strikeout rate.
Comparing to all relievers who threw at least 50 innings, Gregerson ranked 21st out of 132 in wOBA allowed and 55th in strikeout rate. Giles, who saved 15 games for the Phillies, ranked 27th in wOBA allowed and 22nd in strikeout rate.
Overall, Gregerson is probably a middle-of-the-pack closer but a quality reliever. You really have two pitchers who were about equally effective. Giles' 1.80 ERA is misleading because he gave up nine unearned runs. Giles gets a few more strikeouts and walks more guys while Gregerson gets more ground balls.
Is A.J. Hinch better off using one guy in the eighth and one in the ninth? I'm not sure it matters all that much. Even though Gregerson drops down he doesn't have a platoon split: Over the past three seasons he has allowed a .587 OPS to left-handed batters and .582 to right-handers. So Hinch should feel comfortable bringing him to face a left-hander, even if a runner is on base. You can argue that Giles is better for the eighth because he's more likely to escape a jam with a strikeout. But you can argue that Gregerson is better for the eighth (or even the seventh) because he's more likely to get a double play if one is needed.
In general, the Astros' bullpen just needs to be more clutch. While it ranked sixth in the majors in ERA, it ranked 19th in win probability added, so it didn't do its best pitching in close games. It also tired down the stretch, posting a 4.74 ERA in September. Giles will help in that regard simply by adding more depth.
Anyway, most managers love that flamethrower in the ninth, so Giles probably ends up with the closer role. But it's Gregerson, pitching with inherited runners and often against the meat of the lineup, who may have the bigger impact on the Astros' win-loss record.