Tanner Rainey Is the Lowest-Leverage Reliever in Baseball

I typed the command “high-leverage reliever fangraphs.com” into Google over the weekend and set the search range to the past month. About 130 results came up. Next, I ran the same search, except with “low-leverage reliever” instead. This time, Google told me there weren’t “many great matches” for my search and suggested I try “using words that might appear” on the page I was looking for. Message received, Google. Apparently, our coverage here at FanGraphs is biased toward players who actually hold meaningful influence over the outcomes of games. That just won’t do!

All joking aside, there’s a very simple reason we don’t write about low-leverage relievers that often. Low-leverage relievers don’t really exist, at least not in the same way high-leverage relievers do. For one thing, relievers are naturally going to enter games in higher-leverage spots because pitchers are more likely to exit games in higher-leverage spots. The average leverage index when entering games (gmLI) for relievers this season is 1.12; that’s 0.12 higher than a perfectly average-leverage spot. Moreover, the low-leverage relief opportunities do exist are more likely to go to the revolving door of replacement-level arms at the bottom of each team’s bullpen depth chart, rather than an established pitcher whose full-time job is that of a low-leverage reliever. Consider that the median gmLI for active, qualified relievers this season is 1.21. By design, most relievers who stick around long enough for you to know their names are going to be pitching in higher-leverage spots. Yet, that doesn’t mean there aren’t any full-time low-leverage relievers. If anything, it just means those guys are more unusual – and therefore pretty interesting.

With all that in mind, I set out to find a low-leverage arm worth writing about. The qualified reliever (0.3 IP per team game) with the lowest gmLI this season is Thyago Vieira, with a 0.29 gmLI. That would be the lowest gmLI in a season for a qualified reliever since rookie Johan Santana’s record-setting 0.27 gmLI in 2000. Yet, with all due respect to Vieira, he’s hardly the most fun part of that fun fact. (Although, if Vieira goes on to win two Cy Young awards and a Triple Crown I will gladly eat my words.) The 31-year-old Vieira perfectly fits the mold of the replacement-level/revolving-door reliever I described above. He has played for the Brewers, Orioles, and Diamondbacks this season, and he’s currently on the restricted list at Triple-A in the D-backs organization. It seems highly unlikely he’ll get back to majors and pitch the necessary 10.2 innings he would need to remain qualified at season’s end. And, unfortunately, his 0.29 gmLI isn’t nearly as noteworthy without the “qualified” qualifier. If I lower the threshold to 30 innings pitched, 25 other relievers have had a lower-leverage season on record (since 1974).

Funnily enough, however, it was when I looked just beyond the qualified names that I struck gold iron (help me out here metal enthusiasts, is that the right metaphor?) in my search for low-leverage relievers. Tanner Rainey of the Nationals is in the midst of what could be the lowest-leverage relief season of all time:

You won’t see Rainey on our reliever leaderboards unless you play with the “Min Playing Time (IP)” toggle, but he’s only one inning away from qualification. Presuming he continues to pitch exactly one inning per outing, as he has in 33 of his 34 appearances, he’ll need to make 14 more trips to the mound over Washington’s 43 remaining games. That’s more than doable. And if he were qualified right now, his 0.09 gmLI would easily rank as the lowest for a qualified reliever on record:

To keep this up, Rainey will need to continue pitching in low-leverage spots, which is far from a guarantee. The Nationals have more high-leverage innings to go around now that Hunter Harvey and Dylan Floro are wearing new uniforms, and manager Dave Martinez suggested at the deadline that Rainey could see some of those opportunities. That hasn’t really happened yet – Rainey hasn’t pitched in so much as a medium-leverage spot this year – but he has made two of his four highest-leverage appearances in the two weeks since the trade deadline, with his highest-leverage entrance of the season coming on Saturday (gmLI 0.61). It was the second time all year that he entered a two-run game.

Yet, even if Rainey makes another 14 appearances and every single one of them starts in a similarly leveraged spot, he would finish the season with an average gmLI of approximately 0.25. Take that number with a grain of salt, since I made some big assumptions to get there, and because leverage index stats will be adjusted at the end of the season to account for the 2024 run environment. Still, my point stands that we could be watching the least consequential relief season in recorded history. And to think, the fools in Big Baseball Media are too busy paying attention to Shohei Ohtani’s quest for a 40-40 season to even notice.

One reason I’m so fascinated by Rainey’s season is that an average leverage index this low isn’t something that happens by accident. Rainey is the exception to the rule that low-leverage relievers don’t really exist. He has been in the Nationals bullpen all year, and his role has been pretty darn consistent. The right-hander has yet to enter a tied contest or a one-run game. Meanwhile, in 27 of his 34 appearances, he has taken the ball with the Nationals trailing by at least three runs. He has entered with a deficit of at least six runs on five separate occasions, and Washington’s average deficit when he enters a losing game is 4.9 runs. To be fair, the Nationals’ -60 run differential suggests their relievers are probably entering with a deficit more often than not; even so, Rainey is clearly reserved for the worst of it. The team is 7-27 (.206) in his appearances and 47-38 (.553) in the rest of its games. Washington’s run differential upon his entrances is a dismal -100. On a small handful of occasions, Martinez has gifted Rainey the opportunity to pitch with a lead. The catch, however, is that Rainey only seems to be allowed to enter late in games if the Nationals have already scored at least 11 runs and hold at least a six-run lead:

• Rainey enters in the 9th with the Nationals up 11-1
• Rainey enters in the 8th with the Nationals up 11-5
• Rainey enters in the 9th with the Nationals up 14-6
• Rainey enters in the 9th with the Nationals up 14-3
• Rainey enters in the 9th with the Nationals up 11-5

What’s more, Rainey usually comes on to record the final three outs of a game that all but officially has been decided. He has been his team’s final pitcher in 26 of the 34 games he has appeared in this year, which puts him 24th among all relievers in games finished. Every pitcher ranked ahead of him is undeniably a high-leverage arm; they all have had at least 14 save opportunities, and they all boast a gmLI well above average. Rainey, on the other hand, hasn’t pitched in a consequential spot all year. Not only is he 0-for-0 in save chances, but he doesn’t have any wins, losses, or holds. And while he has had his fair share of good and bad outings, he is the only reliever in the sport this year (min. 30 IP) with no shutdowns or meltdowns – games in which he increased or decreased his team’s chances of winning by at least 0.06 WPA. If he keeps this up, he’ll be the first reliever since Chris Beck of the 2018 White Sox and Mets to pitch at least 30 innings in relief without either a shutdown or meltdown outing.

Rainey is not a mop-up man; he usually pitches only one inning, and it’s almost always toward the end of the game. Nor is he a fungible arm at the bottom of the depth chart; the Nationals have stuck with him all season despite his consistently poor results (5.66 ERA, -0.2 WAR). No, Rainey is what I’m going to call a “farther,” since the better opposites of the word “closer” — “starter” and “opener” — have already been taken. It’s a term that only works in writing, but at the same time, it’s an apt description of his job. Rainey pitches only when his team is too far ahead or too far behind – and it’s too late in the game – for his performance to really matter.

Rainey was once a promising reliever. He turned heads in 2020 (2.66 ERA, 42.7% strikeout rate), and after a difficult ’21 campaign, he looked sharp again in ’22. He was the Nationals’ closer over the first half of that season (12 saves, 1.72 gmLI), before Tommy John surgery knocked him out for second half and almost all of ’23. More than two years removed from his surgery, Rainey no longer looks like the same pitcher. His four-seam fastball velocity is down by about three miles per hour, and his slider no longer moves like it once did. From 2020-22, the pitch modeling systems loved his fastball (133 Stuff+, 68 botStf) and his breaker (131 Stuff+, 55 botStf). This year, neither pitch grades out nearly as well.

Perhaps the Nationals have shoehorned Rainey into the lowest-leverage role possible because they’re holding out hope his stuff will return to pre-TJ levels. Or perhaps they’re giving him late-game opportunities as a genuine sign of (misguided) respect toward the former closer. Either way, Washington clearly wants to keep him on the major league roster rather than risk losing him to another organization. If he has stuck around this long, he’s probably safe for the rest of the year. And if Rainey is safe for the rest of the year, he’s got a pretty good chance to pitch the least meaningful full season any of us have ever seen.