With Zack Wheeler joining the Mets’ small army of pitchers on the disabled list, the team will turn to 23-year-old Chris Flexen tonight against the Padres. Unless you’re a Mets fan with a deep interest in prospects, there’s a good chance this is your first time hearing Flexen’s name. I’ll admit that I was unaware of him until a couple of days ago when I came across his name while formatting KATOH’s most recent top-100 list.

But despite his obscurity, Flexen has undeniably earned this opportunity with the way he’s pitched this season. He started the year on the DL after having a bone chip removed from his right knee, but has been utterly dominant since returning. In three High-A starts, he pitched to a 2.81 xFIP with a 25% strikeout rate. He was even better in Double-A, spinning a 2.43 xFIP thanks to a 29% strikeout rate.

It’s been a long slog for Flexen, who was originally drafted by the Mets in the 12th round way back in 2012. After a couple of lackluster seasons in the lower levels, he underwent Tommy John Surgery in 2014. He pitched decently in 2016, his first full year after the surgery, but did so with a sub-17% strikeout rate. There was little reason to suspect he was on the verge of a breakout in 2017.

Eric Longenhagen included Flexen in his preseason Mets list, but only in the “Honorable Mention” section. He saw him as being worse than a 40 FV — the equivalent of a spot starter or middle reliever.

He sits 91-94, touching 96, with an average curveball and fringe change. He has a big, sturdy, inning-eating frame but has already had a surgery, and there are scouts who’d like to see if the fastball plays consistently at 96 out of the ‘pen . Others think he’s more of an up-and-down starter.

Eric provided an updated scouting snippet last month.

He has been 92-96, flashing an above-average slider and throwing all four of his pitches for strikes.

Because of scouts’ pessimism, there’s a sizable gap between Flexen’s stats-only KATOH forecast and KATOH+, which incorporates his (lack of) preseason prospect rank. The stats-only version projects him for 5.6 WAR over his first six years, which is good for 66th overall and 13th among pitchers. But that forecast drops to a meager 2.8 WAR once the scouting data is layered in. KATOH+ sees him as a near-certain fringe-player.

And since it looks noticeably different, I also made a stats-only graph. This one gives him a much more realistic chance of racking up more than 4 WAR.

To put some faces to Flexen’s statistical profile, let’s generate some statistical comps. I calculated a Mahalanobis distance between Flexen’s 2017 numbers and every historical season since 1991. In the table below, you’ll find the 10 most similar seasons, ranked from most to least similar. The WAR totals refer to each player’s first six seasons in the major leagues. Please note that the Mahalanobis analysis is separate from KATOH. KATOH relies on macro-level trends, rather than comps. The fates of a few statistically similar players shouldn’t be used to draw sweeping conclusions about a prospect’s future. For this reason, I recommend using a player’s KATOH forecast to assess his future potential. The comps give us some interesting names that sometimes feel spot-on, but they’re mostly just there for fun.

It’s tough to know what to make of Flexen. While his small-sample 2017 numbers have been exceptional, he’s never pitched anywhere near this well before, nor was he ever seen as much of a prospect. But then again, this might simply be an instance of Flexen finally being healthy for the first time in at least three years. I look forward to watching tonight to see how he fares against big-league hitters.