SAN DIEGO -- The Padres pushed their winning streak to seven games Saturday night behind a guy who didn't know he'd be a Padre until Opening Day.

For a new kid in town, Rob Bowen is making quite an impression.

Claimed off waivers from Detroit, which had him less than a week, Bowen's arrival on Opening Day led to Scott Cassidy's demotion to Triple-A Portland for a few frustrating days. The two were smiling at neighboring lockers after Bowen's first walk-off homer of his life handed Cassidy his third win in four days, a 2-1 decision over the reeling Cubs at PETCO Park.

After Jake Peavy and Cubs skyscraper Sean Marshall dueled for six innings, yielding a run apiece, it was left to the Padres' deep and resourceful bullpen to shut down the opposition until the offense broke through.

Following Alan Embree, Scott Linebrink and Trevor Hoffman to the mound, each delivering a scoreless inning, Cassidy put away the Cubs in the 10th and watched Bowen step up against Bob Howry (2-1) and drill a slider just over the scoreboard in right, sending 37,745 fans home.

"That's huge for us," said Bowen, who is 3-0 as a starter and figures to be behind the plate on Sunday catching Woody Williams. "It shows the character of your club when an individual day after day gets hits in the clutch. This is nice."

As exhilarating as it was for Bowen and for Cassidy, men who savor every day in the big time, it was a night of achievement for Peavy, the club's 2005 All-Star right-hander, in a different manner.

With his high-octane stuff riding out of the strike zone as often as not -- only 62 of his 112 deliveries were strikes -- Peavy used his guile and intelligence, coupled with the wisdom of catcher Mike Piazza, to survive disturbance after disturbance.

"These nights are as gratifying as the nights you have great stuff and mow them down," Peavy said. "I worked for all 18 outs. They had runners in scoring position every inning but one [a 1-2-3 fifth]. It's gratifying to know we battled, got through it and won the game.

"Mechanically, I was out of sync. I think that probably had a lot to do with my control problems. When you're not throwing strikes early in the count, it makes it hard to be as aggressive as you want to be."

The only Chicago run was provided by Aramis Ramirez with a homer to left-center leading off the fourth. The Cubs left runners at third in the first, second and fourth innings, Peavy finding pitches when he needed them and some quality glove work, as well.

Mark Bellhorn saved a run at first with a stab on Jacque Jones' ball headed down the line in the first, and Marshall sent Mike Cameron on his horse to run down a deep drive in the second, leaving Cubbies at second and third.

Marshall surrendered two walks but no hits until Eric Young slashed a one-out single in the sixth. Cameron's infield hit was followed by Brian Giles' game-tying RBI single to right.

It stayed that way until Bowen -- who replaced Piazza in the seventh inning -- walked up in the bottom of the 10th and sent everybody home.

Bowen said he was looking for something to hit hard but wasn't sure what to expect when he smashed Howry's hanging slider on the inner half of the plate.

"In this park," he said, grinning, "you never know. I'm sprinting all the way around [the bases] until they tell me it's a home run."

It was his first homer as a Padre and his second in 55 Major League at-bats.

"I've never hit a walk-off [homer]. I've hit go-ahead homers as a visitor, but I've never had a walk-off. This is nice."

A switch-hitter born in Texas but raised in Indiana, Bowen caught a total of 24 games for the Twins in 2003 and '04 but spent all of last season in Triple-A Rochester. Detroit claimed him on waivers and tried to slip him through waivers to send him to Toledo, but the Padres put in a claim -- and got more than they anticipated, by all accounts.

Billed as a solid defensive catcher with some pop but an unimpressive .238 career average in the Minors, Bowen has looked like a smart, talented hitter -- and it shows in his .389 average, .667 slugging and .478 on-base marks in 18 at-bats.

Similarly productive in his role has been Cassidy, who rebounded from a disappointing performance in Los Angeles, giving up a lead for Chris Young, to pitch effectively the past two nights and nail down back-to-back wins.

"Fortunately, I got that win [against the Dodgers Wednesday night] when I pitched terrible," he said. "That was the bright side of a bad day. If you're here the whole year, you're going to throw 50 games probably. You can't dwell on it when you have a bad game. Whatever you did that day is irrelevant the next time out."

Appearing in a staff-high 16 games, with a 1.08 ERA to go with his 3-0 record, Cassidy has come a long way from that early April demotion.

"This sure beats the first couple weeks when we were losing," he said, his club having rolled a lucky seven.