DENVER -- Talk about having a dream job. In August, Jason Giambi was told to stop coming to work by his then-employer, the Athletics. And he was thankful.

It freed him to enjoy a moment like Wednesday night.

Giambi's pinch-hit two-run single with the bases loaded in the eighth inning gave the Rockies the lead for good in their 5-2 victory over the Mets at Coors Field in front of 26,276. The Rockies stayed a game ahead of the Giants in the National League Wild Card chase.

"I definitely was hoping ... Oakland was going to go young, and with that I said I'd like to get an opportunity to go somewhere else and get a chance," said Giambi, 38. "When it came down to it, I signed with this Rockies ballclub. It's an incredible team. I love their energy."

The Rockies once again fed off the power pitching of emerging star right-hander Ubaldo Jimenez (13-10), who held the Mets to two runs and five hits in eight innings. Jimenez is usually a strikeout pitcher, but he fanned just four and forced 15 ground-ball outs.

After splitting home-and-home showdowns with the Giants' Tim Lincecum in his previous two starts, Jimenez found himself in a tussle with Mets starter Tim Redding (6 2/3 innings, two runs, seven hits).

"There's no small enemy," said Jimenez, who pitched six or more innings for the 24th consecutive time and is 7-1 in his past 10 starts. "[The Mets] don't have a good record, but that's when you have to really focus and try to win. They're going to do everything possible to take it away from you."

The only blip came when Huston Street, who has converted all but one of his 34 save chances, couldn't pitch the ninth because of biceps tendinitis. Franklin Morales pitched a perfect ninth with one strikeout for his first Major League save.

Giambi was struggling at .193 for an Athletics team that knew long ago that the regular season would be its only season. Since joining the Rockies on Tuesday, however, Giambi has basked in ovations before his two plate appearances, then earned cheers with the results.

Giambi drew a bases-loaded walk in Colorado's 8-3 victory over New York on Tuesday. On Wednesday, he replaced second baseman Clint Barmes with one out in the bottom of the eighth and the score tied at 2 and singled to center off Brian Stokes (1-4) to drive in Troy Tulowitzki, who had walked, and Brad Hawpe, who had doubled to left.

"You never know when he's going to take [pitches] and give you a patient at-bat," said the Mets' Gary Sheffield, a teammate of Giambi's with the Yankees a few years back. "Like tonight, he came out swinging."

Tracy said: "You know what's very interesting to me about two days with Jason Giambi? You can see why he is spoken so highly of wherever you go. Ask anybody that has been a teammate of him."

Yorvit Torrealba's RBI single extended his career-best hit streak to 12 games and gave the Rockies a three-run lead.

For all the excitement over Giambi, however, the Rockies' lead isn't any bigger than it is because the Giants beat the Phillies, 4-0, behind their own September addition -- right-handed pitcher Brad Penny, who threw eight scoreless innings.

Rockies manager Jim Tracy, already on record as not caring who the Giants or NL West-leading Dodgers added, said Giambi's contribution is a tribute to the recent pickups Rockies general manager Dan O'Dowd has made.

Right-hander Rafael Betancourt, from the Indians, and left-hander Joe Beimel, from the Nationals, joined the team in trades near the non-waiver deadline. Giambi was signed recently and is in the Majors after a brief adjustment period at Triple-A Colorado Springs.

With right-hander Aaron Cook nursing a sore shoulder, the Rockies are counting on another pickup -- righty Jose Contreras from the White Sox -- as Saturday's starter against the D-backs.

"Those are the type of resources when you're in a position we're in at this point in time in the season, obviously, that turn up huge," Tracy said.

The Giambi move had its fingerprints on the entire game. Having him frees Tracy to use outfielder Seth Smith more regularly in the starting lineup, because Giambi can replace his bat off the bench. Smith hit his 12th home run of the season, a solo shot off Redding in the first inning to tie the game at 1.

Then Jimenez dominated the game, until Giambi could win it.

After Jimenez hung a slider to Jeff Francoeur, who hit it for his 12th homer of the season in the fourth, he gave the Mets little opportunity.

"I really believe that if you go back to the first-pitch breaking ball that he threw to Francoeur that got hit out of the ballpark, from the fourth inning on, that is the only bad pitch that he made," Tracy said.