Paul Maholm pitched well enough to win. He just didn't go deep enough into the game to lock it down.
Maholm was OK with it, though. He still has plenty of confidence in relievers Evan Meek and Chris Resop.
"We had the game and let it get away from us," Maholm said. "But you know what? I'll hand the ball to Meek every time. Everybody is going to have bad outings."
The Cubs trailed by three before scoring five time in the bottom of the eighth to pull out the 5-3 victory Saturday at Wrigley Field.
Chicago broke through as Meek (0-1) walked pinch-hitter Kosuke Fukudome and threw a wild pitch before Starlin Castro hit an RBI double to make it 3-1. Lyle Overbay then misplayed Marlon Byrd's grounder for an error as Castro scored to make it 3-2. Alfonso Soriano tied it with an RBI single and then Blake DeWitt hit a go-ahead two-run double off Resop.
Meek said a mix of poor pitch selection and a lack of command contributed to the meltdown. Of the five runs he was charged with, three were unearned.
"When you go out there and walk the leadoff guy, it's never a good sign," Meek said.
"I go out there every day expecting to get three outs and get them quickly. ... It's a very confident feeling, so going out there and not doing my job and not making the pitches, walking the leadoff guy, that weighs on you hard. Your team got three runs on the board, your starter did a great job and you're expected to get three outs. It just wasn't a good day for me."
Pirates manager Clint Hurdle saw the loss as a learning experience for his young club, adding now the important thing is to win the series. Pittsburgh captured the season opener 6-3 Friday.
"We had shots, just didn't get it done," Hurdle said. "We didn't put a ballgame away. We've got to do that."
Sean Marshall (1-0) got the victory with a scoreless eighth and Carlos Marmol pitched the ninth for his first save.
Zambrano walked two in the top of the first before Pedro Alvarez pulled a two-out RBI single to right to give the Pirates an early 1-0 lead.
Neil Walker, who'd hit a grand slam in Pittsburgh's win Friday, had an RBI double in the third after Jose Tabata reached on an infield single. After Andrew McCutchen walked to put runners at first and second with no outs, Zambrano averted a big inning. He struck out Overbay and then raced to cover first and complete a double play that was started by first baseman Carlos Pena on Alvarez's broken-bat grounder.
And Maholm kept the Cubs off balance. He retired the first eight batters.
"Am I happy that I got through 6 2-3 with no runs? Yeah, but we ended up losing. I'm not the happiest camper right now. It's one of 34 or 35 starts," Maholm said.
"We'll build and see where we're at."
NOTES: Matt Garza, who will make his Cubs' debut Sunday, spent part of Saturday leading cheers on the dugout steps while wearing sunglasses and a sweat shirt. ... Jones had a quick start last season when he hit two homers in the opener against the Dodgers. He had four homers against the Cubs last season when Pittsburgh won 10 of 15 games. ... Kerry Wood made his first appearance for the Cubs since Sept. 27, 2008.. ... Maholm was 3-1 against the Cubs last season and 7-2 in his career.