Zack Wheeler headed to injured list with right shoulder fatigue

MINNEAPOLIS — Zack Wheeler is hurt, thrusting into question his status as the Mets’ most likely and best trade chip this month.

The Mets put Wheeler on the injured list on Monday, retroactive to Friday, with right shoulder fatigue, which popped up over the weekend in Miami as he prepared for his first start of the second half. There is no structural damage, a source said, leading to hope that Wheeler will be able to return when eligible next Tuesday (after a team off day Monday), leaving him with a maximum of two starts before the July 31 trade deadline.

“No huge issues other than a little fatigue,” the source said.

Lefthander Steven Matz will replace Wheeler for his start Tuesday night against the Twins. Thanks to an off day Monday, the Mets don’t need a fifth starter until Saturday against the Giants.

Scheduled to be a free agent after the season, Wheeler, 29, had been very likely to be traded by the 42-51 Mets. Getting dealt would benefit Wheeler, too, because that would eliminate the possibility of being tagged with a qualifying offer as he heads to the open market.

Now, even if the best-case scenario plays out — he starts as soon as possible, pitches again five days later and shows he is healthy and able — this IL stint will instill a degree of doubt in teams interested in acquiring Wheeler, a blow to the Mets’ hopes of maximizing the value of their expiring contracts.

Limiting the Mets’ options: Major League Baseball’s new trade rules. In years past, the Mets could have sneaked Wheeler through trade waivers and had until Aug. 31 to move him. Starting this year, July 31 is a hard deadline for trades, with the August waiver process scrapped.

Wheeler’s injury came days after general manager Brodie Van Wagenen, admitting that “we have to face our reality,” acknowledged the Mets will be trade-deadline sellers for the third year in a row. They will focus on moving pending free agents, he said, and are highly likely to keep players such as Noah Syndergaard and Jacob deGrom, who have more years of team control.

Among the other Mets who could be traded: third baseman Todd Frazier, whose contract ends this season, and lefthander Jason Vargas, who has a team option/buyout for 2020. Wheeler was considered the most valuable of that bunch.

An injury also damages one of Wheeler’s most attractive qualities: his recent durability. After making only 17 starts in 2015-17 — he missed two of those seasons — he hadn’t skipped a turn in the rotation since the beginning of last season. Aided by confidence in his health, Wheeler also had been throwing harder than ever, with his fastball averaging 97.1 mph this season, according to Brooks Baseball.

That, along with an untrustworthy bullpen, led to the Mets riding Wheeler hard this year. They finagled their rotation this month to get Wheeler an extra start before the All-Star break, and he led the rotation with 19 games in the first half. Wheeler ranks fourth among major-league starters with 104 pitches per start (with deGrom, at 103, and Syndergaard, at 100, also ranking in the top 10).

Wheeler’s bottom-line numbers this season — 4.69 ERA, 1.28 WHIP — are underwhelming, especially after his second-half excellence last year (1.68 ERA). But some of his peripherals, including strikeout and walk rates and a higher-than-normal batting average on balls in play, suggest a degree of bad luck. For example, his Fielding Independent Pitching mark — which is like ERA but removes defense from the equation — is a much more palatable 3.66. And like pitchers across baseball, Wheeler has given up homers more frequently, a trend he and others chalk up to differences in the baseballs, which are flying out of ballparks at historically high rates.