MLB

Dickey can’t snag 19th win in Mets’ loss to Nationals

One mistake doesn’t kill a pitcher’s Cy Young award hopes, but the numbers are still the numbers.

And the numbers last night showed R.A. Dickey allowing three earned runs over seven innings and receiving his fifth loss this season: Not awful, but also not a Cy Young resume builder.

It might have been different, if not for a flat Dickey knuckleball in the seventh inning that Tyler Moore crushed for a two-run homer in the Mets’ 5-3 loss to the Nationals at Citi Field.

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“It’s not the worst outing to give up three runs in seven innings against that club,” Dickey said after missing in his attempt to tie Nationals lefty Gio Gonzalez for the major league lead in victories with 19. “But at the same time your margin for error is probably minute.”

It came a day after Dickey told The Post he considers Gonzalez his main competition in the Cy Young race. Gonzalez got his 19th win by holding the Mets to one run over six innings on Monday.

But whereas Gonzalez had the benefit of facing the struggling Mets — who last night set a franchise record by scoring three runs or fewer in a 12th straight home game — Dickey had to deal with a Nationals lineup that entered play fourth in the NL with 640 runs scored.

“This is the best lineup I have faced,” Dickey said. “They are just so functional.There’s not really a lot of breathing room, and you know that.”

Dickey’s line included eight hits with three walks and two strikeouts. Dickey’s earned run average inched from 2.64 to 2.68 — still tops in the National League.

“As he always does, you look up and … he leaves the game and you have a chance to win,” manager Terry Collins said.

The Nationals’ go-ahead rally in the seventh started with Kurt Suzuki’s single with one out. Moore entered as a pinch hitter and slugged Dickey’s first pitch over the left-field fence for his ninth homer this season.

Frank Francisco surrendered two runs in the ninth, without recording an out, to give the Nationals their final runs.

Dickey ended with his first loss since the Reds beat him 6-1 in Cincinnati on Aug. 15. The knuckleballer’s last defeat at home had come on July 24, when the Nationals beat him 5-2.

“I had a mediocre knuckleball tonight and had to pitch with it,” Dickey said.

The Mets (65-77) lost their fifth straight and fell to 4-20 at Citi Field since the All-Star break. They are guaranteed a third straight losing series since sweeping the Marlins three games in Miami earlier this month.

Dickey still needs two victories to become the first Mets pitcher since Frank Viola in 1990 to reach the 20-win plateau. Dwight Gooden won 19 games that same year, and no Mets pitcher had topped 17 victories until Dickey’s run this season.

Besides Dickey and Gonzalez, there are other contenders for the Cy Young award that can’t be ignored. Johnny Cueto (Reds), Clayton Kershaw (Dodgers) and Kyle Lohse (Cardinals) all have numbers worthy of consideration. Then you have closer Craig Kimbrel (Braves), who could earn first-place votes.

Dickey figures to receive four more starts, with three likely coming at Citi Field, allowing the crowd to enjoy the ride. Dickey’s next start is scheduled to come at home against the Phillies Monday.

“There was an energy in the park tonight that was different from the last few nights,” Dickey said. “I certainly recognize that and want to say thank you [to the fans] for that.”