By the slimmest of margins, Mets walk off Nats (updated)

NEW YORK - A hanging curveball to a guy who crushes curveballs. A towering drive over the foul pole ruled a home run after an inconclusive review. Two key insurance runs stranded in scoring position. And a two-hopper to short that could've sent the game into extra innings but instead sent the Mets into celebration and the Nationals into yet another demoralized dugout following yet another loss by the slimmest of margins.

Flip any one of those critical moments in the final three innings of tonight's game at Citi Field, and the Nationals walk away with an uplifting victory. Put them all together as is, and you've got the formula for an agonizing, 6-5, walk-off loss.

"The guys are battling, but we've got to finish games," beleaguered manager Davey Martinez said. "It's a nine-inning game. We've got to start finishing games. We're right there, but we've got to win. The bottom line is we've got to start winning games."

The Nationals aren't winning games, not with any regularity. They're the only team in baseball that has yet to reel off a modest, three-game winning streak. They've been outscored 103-82 from the seventh inning on. They're 10 games under .500, the lowest point they've been since Sept. 2011.

And they feel like it doesn't have to be that way, not if they simply seize control of games at critical moments instead of wilting under the pressure.

"Keep playing until the game's over, and not wait for that moment to happen," catcher Yan Gomes said. "I think mostly the seventh, eighth innings start happening, or when those runs start coming in, we ... I mean, you definitely see a drop. We were still tied, and you kind of saw a drop in our ..."

Gomes didn't complete that sentence, but his sentiment was clear. It aptly described the frantic final three innings of tonight's game, which saw the Nationals take the lead in the top of the seventh and eighth only to give it up in the bottom of each inning, then lose it in the ninth by a matter of inches.

Amed Rosario's infield single with two outs in the bottom of the ninth, in which the speedy Mets shortstop barely beat Trea Turner's throw to first base, brought home the winning run from third base to end this game in dramatic fashion.

Turner, who stayed back to play Rosario's tricky two-hopper, made a strong throw. It would've been enough to retire the vast majority of big league baserunners. But it wasn't enough to retire Rosario, who busted it down the line in a scant 4.02 seconds to beat the throw by a whisker.

"Either stay back and catch it and make a hard throw, or run and kind of make a do-or-die play," Turner said of his two options in that moment. "I guess, looking back at it, you try the other one since it didn't work out. But I felt like I gave myself a chance to make the play, complete the play and get out of the inning."

All of this came after the Nationals bullpen blew leads in the seventh and eighth innings.

Tanner Rainey, the flamethrowing right-hander who impressed in his season debut Monday night, got another chance to impress and protect a one-run lead in the bottom of the eighth tonight. Unfortunately, he left a 98 mph fastball over the plate to Pete Alonso, who promptly launched it to the moon and over the left field foul pole for the home run that yet again tied this game and left the outcome in doubt.

League officials in Manhattan reviewed the play but couldn't find conclusive evidence to overturn the initial call of a fair ball.

"It looked foul," Martinez said. "That's all I could say. Apparently a few people look at it, but it looked foul."

"I had no idea," Rainey said. "I mean, they went to review, and (we're) obviously hoping for the best. But can't do anything about it."

When the Nationals couldn't push across the go-ahead run in the top of the ninth, Rainey got a chance to take the mound again for the bottom of the inning, with Martinez sticking with him over Kyle Barraclough.

"He gave up a home run, I get it," Martinez said. "It stinks, and he doesn't feel good about it. But he struck out the next two guys, which is good. He went back out and got an out. And I thought at 30-31 pitches, he was good after pitching yesterday."

Rainey did strike out Carlos Gómez to open the ninth, but he followed that up with back-to-back walks of Adeiney Hechavarría and Davis.

"I felt like the stuff was there," he said. "But toward the end I started to get away from myself, throwing out of my legs."

With Rainey's pitch count now up to 33 - he topped 32 pitches in three different appearances earlier this season with Triple-A Fresno - Martinez summoned Barraclough from his bullpen, hoping the right-hander could reverse recent history and strand the winning runner in scoring position. (He had allowed 7-of-8 inherited runners to score so far this season.)

Barraclough got Jeff McNeil for the second out of the ninth. And he got Rosario to hit a grounder to short. But that wasn't enough on this night.

What had been a tight, low-scoring pitcher's duel between Erick Fedde and Zack Wheeler turned wacky over the final three innings. The Nationals took the lead in the top of the seventh, only to give it back in the bottom of the seventh. They re-took the lead in the top of the eighth, only to let the Mets re-tie it in the bottom of the eighth.

Brian Dozier's two-run homer in the top of the seventh looked like the much-needed big blast of the night for the Nats. But then Wander Suero served up a three-run homer to pinch-hitter Davis in the bottom of the inning, and now the Mets led 4-3.

No worries, though, because Turner and Juan Soto each delivered RBI doubles in the top of the eighth to put the Nationals back on top 5-4. And yet they stranded two potentially huge insurance runs in scoring position, and wouldn't you know that came back to haunt them.

"We couldn't get those runs in," Martinez said. "You want to get them in. It doesn't happen, but we still got the lead right there."

As much as he's been touted since he was the organization's first round pick in the 2014 draft, Fedde has rarely lived up to the billing as a big league starter. And given the club's more pressing need for relief help, the Nationals decided to make the right-hander a reliever earlier this month and were pleased with the results.

But Aníbal Sánchez's hamstring strain created an opening in the rotation, and Fedde was chosen to fill that slot tonight. The Nats hoped for the best but didn't know for sure what they'd get. What they got was five quality innings and ample reason to give him another opportunity to start.

Fedde was far from perfect; he put seven batters on base and recorded only one 1-2-3 inning. But he kept the ball on the ground, and then his infielders chipped in with one of their best all-around defensive performances of the season.

Anthony Rendon made two nice plays at third base, one of them to ignite a 5-4-3 double play to get Fedde out of a second-inning jam. Turner went way to his right to make a backhanded snag of a sharp grounder and start a 6-4-3 double play to get Fedde out of the fourth. Add a sliding catch in right by Adam Eaton in the third, and the Nationals showed just how much different a pitcher's line looks when he gets help behind him.

The Mets did finally push across a run in the fifth when Dozier couldn't quite make a diving stop of McNeil's sharp grounder up the middle. And Fedde's night would soon be over. Having not thrown more than 49 pitches in any outing in nearly a month, he was pulled with his pitch count at 61 tonight.

"That was his limit," Martinez said. "We talked to him when he came out, and he said he was tired."

"Honestly, I was really hoping for five (innings)," Fedde said of his expectation heading into the start.

The Nationals tried to reward Fedde for his start when they took a 3-1 lead in the top of the seventh. Dozier, who had been 0-for-27 against the Mets this season and hitless in his last 37 at-bats against the boys from Flushing, belted a two-run homer to left off Wheeler. That ignited the visiting dugout, but everyone knew the bullpen still needed to record nine more outs.

The first three of those outs proved quite difficult to record. Suero, who retired the side during a sharp bottom of the sixth, tried to do the same in the bottom of the seventh but couldn't complete the job. He hung a curveball to pinch-hitter Davis, who drove the ball the other way and carried it just enough to clear the right field wall for a devastating, three-run homer.

It's a pitch Suero has been beaten on before, and it's a pitch Davis loves to hit.

"We were trying to expand the zone," Gomes said. "We left it up just enough for him to hit it, and J.D. did what he did. He's a good hitter, and he made us pay for it."

Add it to the list of little things that could've changed the outcome of this game had the Nationals just executed one thing a little better. Add it to a season full of those moments.

"We've been playing a lot better baseball, giving ourselves a chance to win every game," Turner said. "It seems like we're in basically every single game. ... We're in there. We just need to find ourselves on the other side of it. Tonight we didn't do that."