Whether he wanted it or not, Jon Niese has been thrust into the role of Met ace. That’s what happens when you get the nod as the Opening Day starter and then become the stopper after the team loses two in a row. Sure, it was happenstance that Niese took the mound under those circumstances against the Marlins at Citi Field on Saturday afternoon. He was simply starting on his normal four days’ rest. But as natural as it was for him to take the mound, it seems just as natural for him to assume the mantle as the leader of a young rotation that is already minus its nominal ace, Johan Santana, and missing another starter, Shaun Marcum. “When your No. 1 pitcher walks out there your team feels like it has a chance to win. That's what Jon Niese brings to us,” Terry Collins said. “We felt today he was going to give us an outing that was going to give us a chance and he did that. That’s the mentality that he has.” Niese, who has gone six innings or more in 22 consecutive starts, gave the Mets just what they needed, paving the way for a 7-3 victory over the Marlins that ended that two-game skid. Niese went six innings, giving up two runs (one earned) on eight hits, but walked away with a no-decision (reliever Brandon Lyon got the win). Niese got the full Santana treatment of pitching well and getting nothing in return; after he left the game, the Mets exploded for six runs. But he had done his job as stopper.