WASHINGTON -- The New York Mets may not be able to take the possible Matt Harvey shutdown off the back pages of the tabloids. But they certainly made new kinds of headlines Tuesday as they rallied back from a six-run deficit going into the seventh inning to beat the reeling Washington Nationals 8-7.

It was the largest deficit that the Mets have overcome to win a game this season.

"You've got to be kidding me," Mets manager Terry Collins said. "I don't have words for it. I am not sure I have been involved in a bigger win than that. There is no sense of panic on the bench. It has to do with character. That is a big value of any player. This means a lot to everybody in that room."

Kirk Nieuwenhuis hit a pinch-hit solo homer with two outs in the eighth off Jonathan Papelbon to break a 7-7 tie as the Mets beat Washington for the fifth time in a row.

Collins joined the Mets as a minor league field coordinator in 2010, when Nieuwenhuis played in the high minors for the Mets.

"I feel in love with the way he plays," Collins said.

The Mets (77-61) extended their lead to six games over the Nationals (71-67). It was the first career pinch-hit homer for Nieuwenhuis, who was 2-for-18 as a pinch-hitter this year before parking a pitch from Papelbon into the right field seats before a crowd of 27,507, some of them wearing the orange and blue of the Mets.

Nieuwenhuis last homered on July 12 and has four homers this year in 83 at-bats. He came off the disabled list Sept. 1 after having neck and left shoulder discomfort.

"He has had a lot of injuries. I am really happy for him," Collins said.

The homer capped an improbable comeback as the Mets scored six runs in the seventh to the game at 7-7.

"It was almost hard to believe," Washington starter Jordan Zimmermann said of the fateful seventh, when three Nationals relievers walked six batters.

Shortstop Wilmer Flores had an RBI single against reliever Blake Treinen. Right fielder Curtis Granderson walked with the bases loaded off Felipe Rivero to trim the margin to 7-3. Yoenis Cespedes then lined a three-run double down the left field line with two outs off Drew Storen to cut the margin to 7-6.

After two more walks, Mets first baseman Lucas Duda then drew another off Storen with the bases loaded to tie the game at 7.

The momentum appeared to be on the side of Washington after center fielder Michael A. Taylor had a "Little League" grand slam in the sixth to give the Nationals a 7-1 lead.

With the bases loaded and with one out against Harvey, Taylor hit a sharp single up the middle to score third baseman Yunel Escobar (three hits) and give the Nationals a 4-1 lead.

Mets center fielder Cespedes let the ball get past him and it rolled to the warning track as first baseman Clint Robinson, shortstop Ian Desmond and Taylor all came around to score. Taylor was credited with one RBI on his single while the error by Cespedes allowed the other three runners to cross the plate and up the margin to 7-1.

The hit by Taylor knocked Harvey out of the game. In perhaps one of his last outings of the year due to a possible innings limit, Harvey gave up a career-high seven earned runs and eight hits in 5 1/3 innings while throwing just 74 pitches.

"The ball was coming out fine and everything felt good, I just left way too many pitches over the middle of the plate and they got a lot of contact and the balls went through and went their way," Harvey said.

He has now thrown 171 2/3 innings this year and his surgeon, Dr. James Andrews, suggested he should be limited to 180 this year.

"His command wasn't really good," Collins said. "I think he overthrew a little bit. He was trying too hard; it was human nature. I was very proud of him."

Is Harvey under the impression he has one more start left?

"I have no idea," Harvey said. "Whenever they're ready I'll be ready for it and whatever they decide moving forward I'm ready and I'll make sure I'm ready."

Washington starter Zimmermann allowed one run and three hits with six strikeouts in 5 2/3 innings. "I'm fine with that move," Zimmermann said of being taken out in the sixth with a 3-1 lead after throwing 100 pitches. "It didn't work out for us tonight. I had a lot of three-ball counts. I am fine with that move."

The winning pitcher was Addison Reed (3-2) while Papelbon fell to 3-2.

Tyler Clippard (1.21 ERA) pitched a scoreless eighth for the Mets and closer Jeurys Familia (1.73 ERA) pitched the ninth for his 38th save and got Escobar to hit into a double play to end the game with the potential winning run on first in the person of speedy right fielder Bryce Harper.

Robinson, a replacement for the injured Ryan Zimmerman, had two hits, one RBI and a walk. Second baseman Anthony Rendon and left fielder Jayson Werth had two hits for Washington. Mets third baseman David Wright had two hits.

NOTES: Mets RHP Jacob de Grom (12-7, 2.40) will pitch Wednesday in the series finale against Washington RHP Stephen Strasburg (8-6, 4.35) ... Mets INF Lucas Duda, who came off the disabled list Monday, was in the starting lineup on Tuesday at first base ... New York called up RHP Logan Verrett, INF Dilson Herrera and C Johnny Monell from Triple-A Las Vegas. Manager Terry Collins said RHP Carlos Torres, who injured a calf muscle Monday, would be out at least "one to two weeks." He is 5-6 with a 4.45 ERA in 55 games out of the bullpen ... Washington 1B Ryan Zimmerman was out of the starting lineup Tuesday with "oblique soreness," according to manager Matt Williams. Zimmerman (.249, 16 homers) hurt himself on a swing in Monday but played all nine innings, Williams said. He was not used off the bench Tuesday.