Jonathon Niese spent most of last year pitching Double-A ball in Binghamton. He went 5-1 in seven starts at Triple-A New Orleans and was suddenly thrust into the pennant race with three September starts for the New York Mets.

Heady stuff for a 21- year-old.

The Mets gave Niese a chance to win the No. 5 spot in their rotation this spring but the fact is that they were probably more interested in filling it with a veteran. Former World Series MVP Livan Hernandez got the job and will get the ball Saturday at Florida.

Niese is thus in Buffalo, probably at the stage where his career belongs. He’s the No. 1 pitcher in the Bisons’ rotation and the lefthander will be Buffalo’s Opening Day starter today in Coca-Cola Field against the Pawtucket Red Sox.

The 3:05 game will be Buffalo’s first as the Mets’ top affiliate since 1965. The Bisons had been with Cleveland the last 14 seasons.

“It’s an honor,” Niese said of getting the start. “Last year helps me a lot. I got there [to New York]. The pressures of being up there, I don’t have to go through again. It helps me out here. I’ve pitched in front of a lot of fans, pitched in pressure situations. That’s behind me now. All I’ve got to do is get my work in and hopefully good things happen.”

The ballpark gates will open at 2 p. m. today and all fans will re-

ceive a 2009 magnetic schedule. Pregame festivities will include military tributes and the introduction of Clarence’s Derek Andrews, the 2008 Sports Illustrated Kid of the Year.Gov. David A. Paterson will be on hand as will Sen. Charles E. Schumer, Mayor Byron W. Brown, County Executive Chris Collins and representatives from the Mets.

As part of Opening Day ceremonies, the Bisons are giving away a trip for four to New York, including air fare, hotel and tickets to the Mets’ games against Tampa Bay at Citi Field on June 20-21.

Niese, an Ohio native, was born on Oct. 27, 1986 — oddly enough, the date of the Mets’ victory in Game Seven of the World Series against Boston.

Two of his starts last year in New York had poor results but he threw eight shutout innings Sept. 13 to earn a 5-0 win over Atlanta and finished 1-1 with a 7.07 ERA in his first big-league stint.

The 6-foot-4 Niese was New York’s seventh-round pick in 2005 and has moved up a rung on the Mets’ ladder every year.

He went 11-9 at Class A Hagerstown in 2006 and 11-7 at Class A St. Lucie in 2007. He was only 6-7 in 22 starts at Binghamton in 2008 but had a solid 3.04 ERA, then went 5-1, 3.40 at New Orleans.

Niese is far from overpowering, with a fastball in the 90-92 mph range. But he has solid offspeed pitches that can keep batters at bay, topped by a sharp curveball. He combined for 144 strikeouts and just 56 walks in 164 innings in the minors last year.

“My command needs to be consistent,” Niese said. “I think my stuff could get worked on more but there’s things I don’t want to change. I have confidence in every pitch, want to keep good fastball command. My curveball is a pitch I need to keep working on. If I stop working on it, I’ll lose it.”

Niese had a 6.75 ERA in three Grapefruit League starts this year, striking out seven and walking seven. The Mets sent him to minor-league camp in mid-March to make sure he got his work in, calling an early end to the competition for No. 5.

“I understood where they were coming from,” he said. “They told me I had to get my work in and they felt they would cut me short if they didn’t send me down. It was good. I got my work in, and I’m ready for the season.”

“If you tell me that Jonathon Niese is going to pitch in the major leagues tonight, I’d feel very comfortable,” Mets General Manager Omar Minaya said when Niese was returned to the minor-league side. “We could have easily kept him here longer.”

In his final spring start for Buffalo, Niese pitched six shutout innings April 1 in an 8-0 victory over Memphis, the Cardinals’ Pacific Coast League affiliate.

“He’s got a nasty breaking ball,” Bisons manager Ken Oberkfell said. “His last couple outings of the spring, he threw real well for us. I’m counting on big things for him [today]. I think he’s the type of pitcher who will keep us in the ballgame and give us an opportunity to win.”

“Spring was fun,” Niese said. “I got a lot of work in. It was a good opportunity to compete for the fifth spot. Obviously, I came up short but I’ll be working hard here to get back up there.”