The Situation: Zack Wheeler has hit the shelf with a “stress reaction” in his right arm (plz do not call it a stress fracture). The Mets are quickly running out of arms to plug into their beleaguered major-league rotation (ah the halcyon March days waxing about their pitching depth), and have turned to Chris Flexen, who might be their best pitching prospect period. He is certainly the closest to the major-league ready despite tossing just 48 innings above A-ball.

The Background: The Mets selected a 17-year-old Flexen in the 14th round of the 2012 draft as a California prep arm, eventually signing for an over-slot $374,000. He progressed to full-season ball as a 19-year-old in 2014, showing low-90s velocity and a potential plus curve, before his season was cut short by a torn UCL that required Tommy John surgery. He returned to the mound in late-2015, but scuffled in A-ball for the next season-plus. The Mets added him to the 40-man roster after 2016 anyway, but his 2017 campaign was delayed by Spring knee surgery to remove a bone chip. He hit the ground running in May, dispatching with a St. Lucie rehab assignment, before dominating the Eastern League to the tune of a 1.66 ERA and near-30 percent K-rate.

Scouting Report: Despite his sketchy health history, Flexen certainly looks the part of a major-league innings eater. He has a bit of a body-by-Broxton thing going on with a big waist and huge thighs, which will always melt my heart as an evaluator. The delivery is pretty easy, average tempo, average arm circle, high-three-quarters slot, no obvious red flags. Flexen is also a better athlete than the frame would suggest. He’s a pretty good hitter, and fields his position well. That’s not why he is in the majors of course (although the Mets could use an extra stick). Flexen broke out in 2017, as his velocity ticked up to the mid-90s and—shock of shocks—he started flashing a plus slider after his first major league camp. He can throw the fastball to all four quadrants effectively, although command covers for only average movement.

He will also show a two-seamer with a bit of armside and sink for a different look. The slider is inconsistent; it can touch 88 and it will show the usual Warthen movement, but the shape varies and can get slurvy when he tries to spot or backdoor it. That version is still an effective offering though. He’ll slip in a 12-6, upper-70s curve for a different look for lefties or to steal a strike here and there. It’s a potentially average pitch. Flexen is confident throwing either breaker in any count. The change is a clear fourth pitch at present, although it features big velo separation. Overall. the stuff is role 55—mid-rotation dude—but given the durability questions, he might fit best in the late innings, like, well…Jonathan Broxton.

Immediate Big League Future:. Wheeler was likely bumping his innings limit soon, notwithstanding this latest arm issue. Noah Syndergaard and Matt Harvey have just started playing catch. Robert Gsellman is starting a rehab assignment, but there is nothing other than Rafael Montero stopping the Mets from giving Flexen ten starts in the majors to see what they have. The fastball/slider combo is enough to get major league hitters out in the short term, but I don’t know if there is enough of a complete arsenal to go through the order multiple times yet. Costs nothing to find out, but the profile may be more of an inefficient backend type for now. —Jeffrey Paternostro

Fantasy Impact: Flexen fits the mold of a legitimate pop-up prospect, with a scattered injury history that includes Tommy John surgery and therefore has conspired to keep him relatively far off the radar. Anything involving Mets pitchers, especially those with a scattered injury history, should raise the hackles of fantasy players far and wide at this point. But medical files are not the only #beefy thing about Flexen, you see, and he has thus far this season corralled that girth exquisitely and consistently to produce unimpeachable performance. The stuff isn’t top-shelf, but his fastball does have some hop, and his slider does have some bite, and mid- and upper-minors hitters haven’t been able to figure him out for anything across ten starts.

Given the Matthew Lesko suit Zack Wheeler’s once again rocking, there’s a non-zero chance that Flexen takes the opportunity and runs for the next couple months, and that makes him interesting. This is a tailor-made situation for statline scouters to end up bound for disappointment, and one of them in your league will probably bid way too much to find that out firsthand. But with expectations set for a serviceable back-end flyer in a medium-depth league – who can pile up a few whiffs for you, at that – there’s a solid case to be made for moderate FAAB investment at this stage of the season. —Wilson Karaman

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