David Peterson tossed a career-high seven innings and earned the win in the final start of his rookie season Thursday night, when Robinson Chirinos homered and collected all three RBIs as the New York Mets staved off elimination from postseason contention by beating the host Washington Nationals, 3-2.

The Mets (26-31) entered Thursday three games behind the Miami Marlins in the NL East and 3 1/2 games behind the San Francisco Giants and Cincinnati Reds in the division.

The Nationals (23-34) must win the final three games of the series to avoid becoming the first reigning World Series champion to finish in last place in its division since the Boston Red Sox in 2014.

Peterson (6-2) allowed one run on four hits and one walk while striking out four. He finished the season by going 2-1 with a 2.00 ERA in his final three starts. His six wins lead the Mets as well as all rookies.

Justin Wilson threw a hitless eighth and Edwin Diaz earned his sixth save despite allowing two hits in the ninth, including an RBI single by Yadiel Hernandez.

The Nationals scored the game's first run in the fourth on a two-out RBI single by Josh Harrison, but the Mets went ahead almost immediately against Patrick Corbin (2-7) in the top of the fifth, when Guillermo Heredia singled and Chirinos homered.

Chirinos, who entered the game with no homers and four RBIs in 67 at-bats this season, extended the Mets' lead to 3-1 by legging out a two-out infield single to score Robinson Cano. Chirinos is the seventh Mets position player to record at least three RBIs from the ninth spot in the batting order and the first to do it while accounting for all of New York's runs.

Dominic Smith went 3-for-5 with a pair of doubles while Cano and J.D. Davis each had two hits.

Harrison had two hits for the Nationals.

Corbin allowed the three runs on 10 hits and three walks while striking out three. The dual seven-inning outings by Peterson and Corbin marked just the 10th time this season starters have lasted at least seven innings.