Dempster survived a shaky ninth to pick up his 13th save and preserve a win for rookie Sean Marshall, as the Cubs topped the Houston Astros, 1-0, on Wednesday night to avoid being swept. Marshall, Dempster and Bob Howry combined on the seven-hit shutout.

"I was nervous out there today, I'm not going to lie," Dempster said. "I was scared what might come crashing down if I blew that one."

In Dempster's last outing, on July 1 against the Chicago White Sox at Wrigley Field, fans littered the field with trash after he blew a lead in the ninth.

This wasn't a picture-perfect save. Dempster walked leadoff batter Orlando Palmeiro and one out later gave up a single to Craig Biggio. But he got Chris Burke to pop up and Morgan Ensberg to hit into a fielder's choice.

"When I went out there, I was nervous." Dempster said. "[This game] was huge. Those are the kind of things that can get you back in it. It wasn't how I pictured it in my mind when I went out there. The bottom line is win ballgames. It's good for us, a good win."

Cubs manager Dusty Baker didn't hesitate to call on Dempster for the save.

"It was good for everybody's psyche," Baker said of the win. "He walked the first hitter, and you've got [pinch-runner Willy] Taveras running for them, and that doesn't make for a good ending. He made some real good pitches, and we got out of that jam. That's how you get out of slumps and out of streaks ... when you have good pitching. That's what we need."

Marshall (5-7) came through, closing the first half of his inaugural big-league season with a win. The left-hander was making the 31st start by a rookie pitcher this year for the Cubs, second most in the Majors. The kiddie corps now is 6-16.

This also was Marshall's third start against the Astros after losing the first two games. The left-hander gave up six hits and three walks while striking out two over seven innings.

"It feels good to get it under my belt," Marshall said of the first half. "I'm looking forward to getting back out there after the All-Star break."

"We liked him this spring," Baker said of Marshall. "He's had some very good outings and some so-so inconsistent outings, which comes with youth. He had it going tonight. For a young man who's spent very little time in Double-A, he's progressed rather quickly."

In his last start, Marshall gave up four runs to the White Sox over six innings. What was the difference?

"I just made my pitches," he said. "I had the same game plan I had in my last start, but my last start I had poor execution. This start, I made my pitches."

He had another game plan, too.

"I didn't want to lose tonight," Marshall said. "I tried to get the team the win, and we did a great job."

He had to deal with a few jams as the Astros stranded 10 baserunners while he was in the game. They left the bases loaded in the fifth, and in the seventh, Houston had a runner at third with one out, but Marshall got both Ensberg and Lance Berkman to ground out. Right fielder Jacque Jones robbed Jason Lane of a potential extra-base hit with a catch at the wall in the eighth.

"I looked up at the scoreboard and realized they left nine guys, 10," Marshall said. "I tried to make my pitches when I needed to make my pitches instead of giving in to them."

All of the Cubs' offense came in the fifth. With one out, Michael Barrett singled off Roy Oswalt (6-5) and scored on Todd Walker's double. Oswalt struck out six and gave up eight hits in his second complete game.

Dempster needed this.

"After you have a tough outing and you sit in the bullpen and don't pitch, it's tough," Dempster said. "You think about the future and not the past. It's a tough thing, especially when things are going tough. I just kept trying to think positive thoughts.

The Cubs needed it, too.

"We just have to keep winning ballgames," Dempster said. "We know we haven't been playing very good baseball at times. Our approach is to not let the outside stuff bother us and go about what we can control and that's playing baseball."

This story was not subject to the approval of Major League Baseball or its clubs.