CHICAGO — Reed Johnson raised his right arm as soon as the ball left his bat, and he popped out of the dugout moments later for a curtain call.

Alfonso Soriano simply added to the frenzy.

Johnson and Soriano hit back-to-back homers in the eighth, and the Chicago Cubs escaped with an 8-5 victory over the Pittsburgh Pirates Sunday after blowing a three-run lead in the top half of the inning.

The home runs lifted the Cubs to their seventh win in eight games and capped a strange afternoon that saw Carlos Zambrano leave after five strong innings even though he was not hurt.

Chicago (67-45) moved 22 games above .500 for the first time since 1989, when it won 93 games, but what looked like an easy win turned dramatic in the eighth.

The winning rally started when Craig Hansen (0-1) walked Geovany Soto with two outs. Sean Burnett came in, and Johnson drove an 0-2 pitch to left and the celebration started.

Soriano gave the fans more to cheer when he sent a 1-2 pitch from Burnett to the seats in left, making it 8-5. Carlos Marmol came in and pitched a perfect ninth for his sixth save in eight chances.

"We've got a lot of guys who come off the bench that I think could start on other teams," Johnson said. "Guys that when they do play, they're always contributing and that's what you want. ... We've got the right guys in this clubhouse."

This time, Johnson came through after Chad Gaudin (3-1) allowed the tying two-run homer to Andy LaRoche in the eighth.

The drama started before the top of the sixth when Cubs manager Lou Piniella decided to bring in Jeff Samardzija even though the Cubs had a 5-2 lead and Zambrano had retired 12 in a row.

Zambrano, who had completed his warmups, left to a standing ovation, raising his right index finger on his way to the dugout.

Samardzija left with one out in the eighth after allowing just one hit while striking out one and walking one in 2Z\c scoreless innings, but Neal Cotts and Gaudin could not hold the lead. Cotts gave up a double to Doug Mientkiewicz. After Nate McLouth popped out, Ryan Doumit singled to right, making it 5-3.

Piniella brought in Gaudin, and LaRoche drove a 3-2 pitch out to left to tie it.

"He threw me three fastballs for balls and then two sliders for strikes so I was pretty sure he was coming with a slider unless he wanted to walk me," said LaRoche, who came to Pittsburgh from Los Angeles in the deal that sent Jason Bay to Boston and Manny Ramirez to the Dodgers before the deadline. "So I was sitting on it and he just threw it right down the middle."

Zambrano allowed just three hits, struck out two and walked one while throwing just 82 pitches after going 4-1 last month.

So why the early exit? The Cubs are trying to preserve Zambrano, who threw 125 and 118 pitches in his previous two starts.

And why did he take his warmups? It was a stall tactic to give Samardzija more time in the bullpen.

"It takes him a little longer to get ready in the bullpen, and that's one of the reasons that when we bring Jeff into a ballgame it's to start an inning because we can't get him ready quick enough in between innings," manager Lou Piniella said. "He wasn't quite ready yet, so we had (Zambrano) go out there and throw seven or eight pitches and wait until we got the call that Jeff was ready to go."

Zambrano allowed an unearned run in the first and a leadoff homer to Brandon Moss — who came from Boston in the Bay trade — in the second — before settling down. The Cubs tied it at 2 in the bottom half and got two more runs in the fourth on consecutive doubles by Jim Edmonds, Soto and Zambrano against Pittsburgh starter Ian Snell to make it 4-2.