Grading the Mets’ Aaron Loup signing

It wasn’t the left handed pitcher we all expected them to sign, but the Mets did add to the bullpen earlier this week, inking Aaron Loup to a one year, $3 million deal. While he’s not a household name, Loup has had a solid career over the last decade, coming up with the Blue Jays and bouncing between the Phillies, Padres, and Rays over the last three years. He has a career 3.38 ERA supported by a 3.50 FIP and, despite being a side-arming lefty, has been a somewhat viable option against right hand hitters over the course of his career (.324 wOBA vs righties, .279 against lefties).

For any pitcher who spends time in Tampa, it’s almost a given at this point that there’s something interesting going on under the surface. For Loup, the adjustment was increased use of his cutter, which he threw almost twice as often in 2020 as he did in 2018 (there was an increase in 2019 while he was with the Padres, but he threw only 3.1 innings due to injury). Using the cutter inside to lefties and away to righties led to Loup’s best year since 2015, as he posted an 85 DRA- while staying relevant despite the new three-batter minimum rule.

Any improvements from 2020 come with a small sample size caveat, and Loup’s performance stretched across only 25 innings. Still, there’s reason to believe that he is closer to who he was last season - a functional 7th inning option - as opposed to his more middle-reliever flavored career prior. Conversely, Statcast pegged Loup as a bit lucky by xwOBA, predicting a .299 mark that’s more in line with the rest of his career. Which of these data is more important? Insert shrug guy emoji here.

Because of how fungible relievers are, evaluations of free agent signings are fairly dependent on how the rest of the market develops. To that end, let’s consider two comparable free agents in Justin Wilson and Jake McGee; 33/34-year-old lefty relievers with the ability to get batters from both sides out and at least some experience in late-inning roles. Wilson and McGee are better by Loup across most of the stats we’d care about - DRA, strikeouts, 2020 performance, and career track record, just to name a few.

It’s difficult to make a definitive argument in favor of one reliever over another in the same general skill-tier, but both Wilson and McGee appear to be at least somewhat better. It would be a surprise to see either sign for much more than what the Mets jut paid Loup given how the market has developed so far. Caveats about teams having more sophisticated models apply, but it seems the Mets made this move to either gamble on a flimsy statistical premise or just to save a few bucks.

At $3 million, it’s virtually impossible to call any move silly because the downside is basically nonexistent, and the Mets certainly needed a lefty reliever. Nevertheless, this doesn’t strike me as a particularly shrewd signing given the other options available. For now, the Loup signing receives a C, pending a re-evaluation at the end of the offseason.