Koda Glover’s Spring Training Dominance Might Not Mean Much

A couple of years ago, the Blue Jays were blown away by the spring training performances of a couple of 20-year-old flamethrowers, and because they were the team’s two best pitchers in the Grapefruit League, the team decided to carry both Roberto Osuna and Miguel Castro on the Opening Day roster. Castro even took over as the team’s closer for the third game of the season; the Blue Jays bet big on talent over experience, and while Castro is a reminder that spring training success doesn’t always carry over to the regular season, the team struck gold with Osuna, who has been one of the game’s best relievers the last two years.

There aren’t any 20-year-olds threatening to crack the end of a contender’s bullpen this year, but over in Washington, the Nationals do look like they’re giving strong consideration to handing the ninth inning job to rookie Koda Glover, who turns 24 a week after the season starts. Like Castro and Osuna, Glover is opening eyes with elite velocity and a fine spring training performance, and since Dusty Baker seems to prefer Shawn Kelley and Blake Treinen in setup roles, Glover is the guy who most looks like a traditional closer, even if he doesn’t have the type of experience that is usually required before earning the job.

Unlike the Toronto pair, Glover already did his A-ball to the Majors climb last year, pitching well at every stop on the minor league ladder before scuffling a bit in the big leagues. But while he ran an ERA over 5.00 in the Majors, and failed to record as many strikeouts as you’d expect with his stuff, it’s also not like he got lit up last year; opposing batters hit just .200/.277/.387 against him, good for just a .284 wOBA. Glover’s minor league performances also suggest the team has some reason to think that this plan might work, as both ZIPS and Steamer think he’s effectively as good as anyone in that bullpen besides Kelley.

And spring training dominance, while often overstated in value, isn’t worth ignoring entirely. As Dan Rosenheck showed a couple of years ago, you can improve pre-season projections by incorporating spring training data, and the effects are largest for young players on whom we have the least amount of big league data, meaning the projections have more room for error. And Glover’s spring numbers thus far are exactly the types of numbers Rosenheck identified as potentially worthwhile predictors of a performance that could be better than the current projections state.

His grapefruit league line, to this point.

8 IP, 4 H, 1 R, 1 BB, 11 K.

The hit and run categories don’t matter much, but that 39% strikeout rate? That’s something to pay attention to. Rosenheck’s study showed that big spikes in spring training strikeout rate did tend to suggest better pitching performances in-season, and all Glover really needs to do to become a high-end reliever is miss more bats. The fact that he’s destroying opposing hitters in spring training should be a very encouraging sign.

But there’s a caveat here, because Dusty Baker has decided to get Glover ready to pitch the ninth inning by having him actually pitch the ninth inning, rather than getting his work in earlier in the game. This means that by the time Glover has pitched, he’s generally been facing minor league hitters, since big leaguers aren’t playing all nine innings in the Grapefruit League. Because MLB.com helpfully has game logs for spring training, we can actually go through and look at the 28 batters he’s faced so far this spring. So let’s do just that.

3/20, NYY: Clint Frazier, Pete Kozma, Billy Mckinney, Kyle Higashioka
3/18, HOU: Max Stassi, Colin Moran, Alejandro Garcia, A.J. Reed
3/16, NYM: Ricardo Cespedes, Jacob Zanon, Andres Gimenez
3/13, DET: Steven Moya, Mike Gerber, Juan Perez, John Hicks
3/10, STL: Breyvic Valera, Wilfredo Tovar, Chad Huffman
3/7, BOS: Mitch Moreland, Chris Young, Jackie Bradley Jr
3/3, MIA: Ryan Jackson, Matt Juengel, Austin Nola, Destin Hood
2/28, HOU: Juan Centeno, Jake Marisnick, Andrew Apin

Among those 28 opponents, exactly four are likely to break camp with a big league team this year, and one of those four is Jake Marisnick, who hits like a minor leaguer. The good news is that, when asked to face the bottom of Boston’s line-up, he struck out all three of the Red Sox big leaguers. The bad news is that I don’t know how much the Nationals have really learned about Glover in the other 24 at-bats, given that we already knew he was capable of blowing minor leaguers away.

So, while it’s better that Glover is carving up the likes of Juan Perez and Matt Juengel than if he was struggling against them, we probably can’t apply Rosenheck’s study directly to Glover’s performance, since most of the players in that study faced mostly big leaguers by playing in the early innings of spring training games. And while Glover didn’t need a big spring training adjustment in order to be a decent enough option to close, the quality of competition should temper the excitement about what he’s done this month.

With a mid-90s fastball and a slider that looks like an out-pitch, the big question facing Glover is probably how well he’ll handle left-handed hitters, which could be the difference between him succeeding as a closer and being more suited to a match-up role. If the Nationals wanted to gather the most pertinent information to help them evaluate his readiness for the closer’s role, they probably should have had Glover face as many big league lefties as possible this spring.

With a few weeks of spring training left, there’s still time for Baker to shift his usage plan, and test Glover against the kinds of guys he’ll actually have to get out if he wants to pitch the ninth inning in D.C. this year. But until that adjustment happens, we probably shouldn’t put too much stock in Glover’s dominant spring training numbers. We already knew he could get low-quality hitters out. If he’s going to be the closer for a contending team, the Nationals need to figure out if he can get big leaguers out too.