CHICAGO – Derrek Lee led off the bottom of the 10th inning with his 10th homer, giving the Chicago Cubs a 4-3 win yesterday over the Mets and saving the Cubs after yet another meltdown by the bullpen.

“I guess we don’t do anything the easy way,” manager Dusty Baker said.

Lee’s homer came on a 3-2 pitch from Heath Bell (0-1) and ended an 11-pitch at-bat. The Cubs, who won for only the third time in 11 games, took two of three from the Mets.

“He just kept challenging me. I’m glad we won. It was cold out there. I’m glad to get it over with,” Lee said.

The game time temperature of 49 degrees was 28 degrees colder than Tuesday night’s game. Coupled with a 14 mph wind blowing in from left field, it had fans bundled up and players blowing on their hands all day.

But Lee, the Cubs’ best hitter all season, got his drive through the wind and just into the seats in left-center.

“You couldn’t get a cannon through that wind, and on the last pitch he was able to do it,” Mets manager Willie Randolph said.

Mark Prior allowed just two hits in seven strong innings for Chicago, but the Mets tied it at 3 on pinch-hitter Eric Valent’s two-out single in the ninth off new closer Ryan Dempster (2-3).

Dempster blew his first save chance of the season, got the win and then went for precautionary X-rays on his right forearm after getting hit by Mike Piazza’s line drive in the 10th.

With the Cubs leading 3-2 in the ninth, Dempster gave up a one-out walk to Doug Mientkiewicz and a single to David Wright before fanning Victor Diaz for the second out. But Valent lined a single to left to tie the game and deny Prior a victory.

It was the second start in a row that Prior pitched a gem, only to have his bullpen cost him a win by blowing a lead in the ninth. Chicago’s struggling bullpen now has five blown saves.

The Cubs loaded the bases in the ninth, but couldn’t score. Neifi Perez hit a comebacker to Bell, who started a 1-2-3 double play that ended the inning. But Bell lost the showdown with Lee in the 10th. After the count reached 3-2, Lee hit five straight foul balls before connecting for the game-winner.

“Right now he’s hitting the ball well and he hit it perfectly,” Bell said. “It’s not a good feeling. I had a pitch on the outside at 2-2 that I definitely thought was a strike. But you can’t blame the umpire. I’m just more disappointed to let the team down.”

Diaz’s bases-loaded double in the second staked Victor Zambrano to a 2-0 lead, but Chicago scored three in the bottom half, taking the lead on Perez’s RBI single.

Prior walked three and struck out seven, retiring 13 straight until Diaz singled with one out in the seventh. And the right-hander might have escaped the second inning if not for the first of two errors by second baseman Jerry Hairston.

Prior walked Cliff Floyd, and Hairston booted Piazza’s potential doubleplay grounder before a walk to Mientkiewicz loaded the bases with none out. One out later, Diaz drove a two-run double off the right-field fence.

The Cubs scored three in the bottom half, thanks to Zambrano’s wildness. Hairston was hit by a pitch, and Henry Blanco’s fly into the wind fell in front of center fielder Carlos Beltran for a single. Zambrano committed a balk, then threw a wild pitch that allowed Hairston to score.

Prior walked, and when Corey Patterson hit a grounder to first, Mientkiewicz stepped on the bag and threw home, but Piazza couldn’t hold it as Blanco scored, tying the game. Perez then singled to score Prior for a 3-2 lead. Zambrano allowed three runs in six innings.