CINCINNATI - Smiling jubilantly, Shawn Estes reared back and gave an emphatic thumbs-up to the dozens of fans chanting his name behind the Cubs dugout.

He felt like he'd just won a playoff game.

Needing a win to keep Chicago alone in first place, the left-hander threw a four-hit shutout that was a career highlight and, perhaps, a defining moment of the Cubs' playoff surge.

With Estes leading the way to an 8-0 victory over the Cincinnati Reds, the Cubs rested their more-imposing starters and preserved their one-game lead over Houston in the NL Central with four to go.

''I feel like I'm on cloud nine, to be honest with you,'' said Estes (8-11), who was demoted to the bullpen in early September. ''It's nice to hear the fans chanting my name out there. It's been a long time. It's very refreshing to hear that kind of stuff.

''We'll see what happens from here on out, but I think we've got the confidence and the momentum right now.''

They've also got Sammy Sosa hitting home runs once again, the one glaring omission from the drive toward their first division title since 1989.

Sosa tied Mickey Mantle for 10th on the career list with his 536th homer, a solo shot that started a six-run third inning. The Cubs' most feared hitter has been trying too hard lately, determined to get a hit that would make a difference in the free-for-all atop the NL Central.

Once he relaxed, he got it done.

''Sometimes when they don't gave you a pitch to hit, you go outside the strike zone,'' said Sosa, who ended a 3-for-22 slump with his 37th homer off rookie Josh Hall (0-2). ''I said to myself, 'I've just got to be patient.' That's what happened.''

There was a lot of pressure on the Cubs when they took the field. They watched television in the clubhouse and muttered cuss words when second-place Houston rallied to beat San Francisco 2-1 in the afternoon, meaning the Cubs had to win to remain one game ahead.

A majority of the crowd of about 30,000 was pulling for the Cubs, who made quick work of the downtrodden Reds. The majors' worst defense made two errors in Chicago's six-run third inning, and Cincinnati was shut down for the second night in a row.

The Reds have managed only six hits while losing the first two games of the series, 6-0 and 8-0.

''Down the stretch here, you're going to win with pitching,'' manager Dusty Baker said. ''The last two days have been awesome. You rarely see back-to-back shutouts.''

The Reds do. They've been blanked eight times since Aug. 8, including consecutive shutouts last month against San Diego and Arizona.

The latest one was hard to fathom. The Reds knew that Estes has a history of control problems - he pitched miserably for them last season - and were reminded before the game to let the left-hander self-destruct.

Instead, they gave him plenty of help.

''The scouting report said make him throw strikes - be patient,'' said Russell Branyan, who had one of Cincinnati's four hits. ''I looked up in the sixth inning and he had like 61 pitches. Either he was throwing a lot of strikes, or we weren't being very patient.''

Estes' last start was Sept. 4, a five-inning performance that got him bumped to the bullpen. He threw two-thirds of an inning in relief on Sept. 19, and that was it.

Baker decided to start him Wednesday so he could give the other starters an extra day of rest for the big games ahead this weekend - three against Pittsburgh at Wrigley Field.

The move worked perfectly.

''One step closer to the finish line,'' Baker said. ''That was huge.''

Notes: It was Estes' 11th career complete game and eighth shutout. He also matched his career high with two hits. … The Cubs had their way against a progression of nondescript pitchers who wore numbers 58, 70, 71 and 50. … Reliever Matt Belisle threw a fastball over Sosa's head in his next at-bat after the homer. Sosa was angry at the time - he was beaned by Pittsburgh's Salomon Torres on April 20 - but later conceded the rookie wasn't trying to hit him. … The Cubs are a season-high 14 games over .500 (85-72). They're 17-6 in September.