MIAMI - Jon Niese chuckled Sunday when informed that Terry Collins said he was going to tell the struggling lefthander that Monday's start against the Nationals "is the biggest game you've ever pitched in your life."

"Yeah, I guess," Niese said.

With the NL East-leading Mets holding a four-game lead over the Nationals, Niese's start obviously is big. It's also big for him because he has a 9.82 ERA in his last three outings.

If you buy the notion that the Mets' six starters are pitching for four possible postseason slots -- we won't get into the Matt Harvey innings-limit mess right now -- then Niese also is auditioning for the chance to get into some truly big games.

But of today's series opener, Niese said: "Just another game. [That's] how I'm going to treat it."

Collins had a choice to start someone else, but Niese has a nice history against Washington. He is 3-4 with a 3.19 ERA against the Nationals and is 2-2, 3.19 at Nationals Park.

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Niese said Collins' words "are not going to get me back to where I was." Asked what might, he said: "Other than [not] giving up five runs in an inning? . . . I've just got to eliminate the big innings."

Niese will be opposed by Max Scherzer. Harvey faces Jordan Zimmermann Tuesday and Jacob deGrom draws Stephen Strasburg on Wednesday.

Trainer's room

Michael Cuddyer (right wrist) had a cortisone shot Sunday in New York . . . Daniel Murphy, who had been out with a strained quadriceps, grounded into a double play as a pinch hitter in the seventh . . . David Wright got the day off so he can play in all three games of the Washington series.