So he asked catcher Travis d'Arnaud and pitching coach Dan Warthen a simple question: "Do you all see anything?" Warthen went into the clubhouse to check some video from Tuesday night's game and noticed Wheeler was "collapsing" instead of "throwing downhill," as the right-hander put it.
Thanks to that mid-game adjustment to his delivery -- and Washington's own miscues, including one runner hit by a batted ball and another thrown out at the plate -- Wheeler pitched 6 2/3 innings to win his fourth consecutive decision, helping the Mets beat the NL East-leading Nationals 6-1.
"I didn't have my best stuff. And it wasn't very fun. But you've got to find a way through it," said Wheeler (7-8), who contributed a broken-bat RBI single at the plate. "You're mad at yourself, and you're trying to figure out what it is. I wouldn't say it's mentally draining, but it's just frustrating."
Relying on a fastball consistently in the high 90s mph because his curveball wasn't working, Wheeler was good enough on a muggy night when the temperature was 85 degrees at first pitch. The righty went 3-8 with a 4.45 ERA in his first 16 starts, but is 4-0 with a 1.59 ERA in seven appearances since June 30.
"This kid has really, really gotten better," Mets manager Terry Collins said. "I mean, as he continues to improve, the sky's the limit."
Said Washington's Jayson Werth: "That was the best I've seen him. I don't know how many times I've seen him, but his velocity was a lot higher than I remember."
Werth led off the sixth with a double. When Adam LaRoche followed with a single to left, third base coach Bob Henley sent Werth home. Left fielder Eric Campbell threw out Werth with a one-hop toss; the call stood after a replay review to check whether d'Arnaud blocked the plate.
Nationals lefty Gio Gonzalez (6-8) was charged with four runs and six hits over six-plus innings. He put two runners on to begin the seventh, then shook his head as he walked off the mound when manager Matt Williams yanked him with Wheeler coming to the plate.
Asked if he was upset that he was removed there, Gonzalez replied: "I wanted to face the pitcher, yes."
Mets: Closer Jenrry Mejia "tweaked his back" in Monday's loss against San Francisco, Collins said, calling the reliever's status day to day. Right-hander Matt Harvey, recovering from reconstructive elbow surgery, threw off a mound for the first time since the operation, and Collins said the pitcher felt fine after Tuesday's session in Florida.
Nationals: Third baseman Ryan Zimmerman, on the DL since injuring his right hamstring July 22, has a grade-three strain and could miss six weeks, general manager Mike Rizzo said. Williams thinks Zimmerman -- who began walking on a water treadmill Monday -- could return during the regular season.
Mets: Wednesday's starter, left-hander Jonathan Niese (5-7, 3.24 ERA), lasted only four innings in his last appearance at Nationals Park, allowing five runs in a 5-2 Mets loss May 16.
Nationals: The Nationals start righty Doug Fister (10-3, 2.68 ERA). Might second baseman Danny Espinosa get back into the lineup after giving way to trade deadline pickup Cabrera? Espinosa is 5 for 12 (a .417 average) against Niese.
WHAT A CATCH:
Mets center fielder Juan Lagares ended the seventh with a head-first diving catch of a sinking liner by Denard Span. Lagares got the wind knocked out of him on the play and was checked on in the outfield by Collins and a trainer but stayed in the game.