PITTSBURGH — Once again, the New York Mets were left out of a party at PNC Park.

The Mets failed for the third straight day to clinch the NL East title when Zach Duke and the Pittsburgh Pirates finished off an unlikely sweep Sunday with a 3-0 win.

"I'm not frustrated. We are a little disappointed we didn't get it done," Mets manager Willie Randolph said. "You want to go out and do it with all the anticipation."

New York was denied its first division title since 1988 later in the day when second-place Philadelphia beat Houston 6-4. The Mets can clinch at home tonight with a win over Florida or a loss by the Phillies.

The Mets came to Pittsburgh with a magic number of one and the best record in the majors. Even with a sizable contingent of New York fans in the stands, the young Pirates became the first NL team to sweep the Mets this season.

Showing their spirit, the Pirates — with the next-to-worst record in the league — celebrated with hearty handshakes on the field. Pittsburgh completed its first three-game sweep at home against New York since 1998.

"When we heard that they had their party planned for this town, we took it kind of personally," Duke said. "We were like, 'Man, everybody just thinks we're going to roll over when they come in here.' But it's kind of a different story for us this half and we knew that if we put our minds to it we could definitely get the job done and we did."

While the sweep won't stop the Mets from eventually reaching the playoffs, it may have exposed a weakness that could prevent them from advancing far once they get into the postseason.

For the third day in a row, a Pirates left-hander beat New York. The Mets have lost 13 of their last 18 when lefties started against them and are 23-21 overall — compared to 67-37 when facing a right-hander.

"It seems like every time we face a lefty, we don't get on base," star Carlos Beltran said. "But we are not concerned at all. We trust in every single one of us in here, and we know this is just something that probably has been a coincidence or something, I don't know. Sometimes we have good games against lefties. Sometimes we don't."

Sunday was clearly the latter as Duke (10-13) allowed eight hits, walked one and struck out six in eight innings. The Mets had only one extra-base hit and never advanced a runner past second base.

Freddy Sanchez had two hits and two RBI and Chris Duffy scored twice for the Pirates. Salomon Torres pitched the ninth for his ninth save.

"I think it's safe to say that this might be the best all-around series that we've played," Duffy said. "Every facet of the game, from pitching to defense and hitting. This is something we've been looking for a while so it feels great. Obviously I'm sure they're not too happy. I'm sure they had some plans.

"The sight of them celebrating on our field, I don't think it would've been a very good taste in our mouths just to see that. This was just a great all-around series," he said.