Rapid Reaction: Mets 8, Nationals 7

WASHINGTON -- Kirk Nieuwenhuis was traded to the Los Angeles Angels in May for cash. He was claimed back off waivers by the New York Mets less than three weeks later, placed through waivers again and sent to Triple-A Las Vegas.

Now he will be remembered as the Met who might have secured the organization's first postseason berth in nine years. He will also be known as the player who delivered the shot that made Matt Harvey's innings cap, at least momentarily, an afterthought.

Nieuwenhuis delivered a tiebreaking, pinch-hit homer in the eighth inning against Jonathan Papelbon, and the Mets stunned the Washington Nationals 8-7 on Tuesday.

By taking the first two games of the series, the Mets (77-61) have opened a commanding six-game lead over the Nats (71-67) in the National League East.

The Mets' magic number dipped to 19.

The commanding division lead should lessen the focus on how many innings Harvey has remaining in the regular season, as the games down the stretch might end up being not all that meaningful.

The Mets, aided by six walks in the seventh from Nationals relievers, produced a six-run frame to even the score at 7. That marked the biggest deficit overcome in a win this season.

The frame included Yoenis Cespedes redeeming himself for a costly fielding error the previous half-inning. It also featured a meltdown by Drew Storen.

Wilmer Flores produced an RBI single, and Curtis Granderson walked with the bases loaded to lift the Mets to within four runs.

With the bases still loaded, Storen entered, and Cespedes greeted him with a three-run double to pull the Mets within 7-6. Storen then walked Daniel Murphy, uncorked a wild pitch and walked David Wright to reload the bases.

That brought up Lucas Duda in his first game since his return from the disabled list. Storen issued four straight balls to Duda to walk in the tying run.

Travis d'Arnaud finally lined out to end the six-run frame.

Cespedes now has 34 RBIs in 35 games with the Mets since he was acquired from the Detroit Tigers.

Earlier in the day, the Mets revealed that Major League Baseball and the Players' Association had agreed to a waiver that would allow the team to continue negotiating with Cespedes once he is released, per his contract, five days after the World Series. Previously, the Mets would have been barred from re-signing him until May 15.

Dark night: In his first on-field chance to calm critics, Harvey looked more mortal than Dark Knight. Harvey was rocked for a career high-matching seven runs in 5 1/3 innings as the Nationals raced to a 7-1 lead.

Harvey allowed four singles in a two-run first inning. The wheels came off in the sixth. With Washington leading 3-1, Harvey surrendered a leadoff single to Yunel Escobar and walked Clint Robinson. Harvey then failed to cleanly field Ian Desmond's bunt with his bare hand. After getting the handle on the baseball, Harvey tried to get the lead runner at third base. The throw was too late, and the bases were loaded on what was ruled an error-free fielder's choice. (That scoring might be changed upon appeal to MLB.)

Harvey rallied by striking out Wilson Ramos, but then things completely unraveled. Michael Taylor singled, and the ball skipped over Cespedes' glove. All three baserunners and Taylor scored on what is unofficially known as a Little League grand slam. (Officially, it was a single and three-base error.) The runs all became earned when Jayson Werth followed with a two-out double against Erik Goeddel.

The seven earned runs charged to Harvey match his career high. He allowed that total May 23 against the Pittsburgh Pirates and June 10 against the San Francisco Giants.

With another 5 1/3 innings added to his odometer, Harvey stands at 171 2/3 innings on the season. He might only get one more start in the regular season, leading into a final-series showdown with the Nationals at Citi Field, in which he would pitch if there is something at stake.

The Mets have resolved to go to a six-man rotation. After Bartolo Colon, Steven Matz, Noah Syndergaard and Jonathon Niese pitch in the next series in Atlanta, it is entirely possible Logan Verrett -- not Harvey -- faces the Miami Marlins on Monday as the Mets open a homestand.

What's next: Jacob deGrom (12-7, 2.40 ERA) opposes right-hander Stephen Strasburg (8-6, 4.35) in the series finale at 7:05 p.m. ET Wednesday.