CHICAGO (AP) — Big Z needs a big outing or the Chicago Cubs’ 100-year wait for a World Series championship could quickly reach 101.

Carlos Zambrano will head to the mound Thursday night in perhaps the biggest game the emotional ace has ever pitched.

That’s because the Cubs got off to the worst possible start against the new-look Los Dodgers, who rode a grand slam from James Loney and homers from Manny Ramirez and Russell Martin to a 7-2 victory Wednesday night in the NL playoff opener.

Only 18 of 56 teams who lost the division series opener came back to win the series, including only four of 28 in the NL, according to the Elias Sports Bureau.

‘‘We definitely don’t want to go down 0-2,’’ Chicago’s Derrek Lee said. ‘‘It’s a short series, every game is huge. There’s no denying that.’’

Loney’s grand slam off Ryan Dempster — who said on the first day of spring training he thought the Cubs would win the World Series — hushed a crowd of 42,099 at Wrigley Field on a windy 53-degree night.

‘‘The atmosphere here was real quiet as I was going around the bases. So I think our fans were cheering back home,’’ Loney said.

The Cubs entered the postseason with the best record in league, hoping for a fast start a century after their last World Series championship. What they got was a performance that, no doubt, produced some ‘‘here we go again’’ feelings from their long-suffering fans.

The Cubs have lost seven straight postseason games, dating back to 2003 when they dropped the final three of the NLCS to the Florida Marlins after holding a 3-1 lead.

‘‘You cannot get too happy and too sad. It’s only one game,’’ Ramirez said. ‘‘We cannot fall asleep with those guys. They’re the best team in the National League and anything can happen.’’

Ramirez’s homer was his 25th in the postseason, extending his own record.

‘‘I’m just being Manny,’’ Ramirez said.

And are the Cubs just being the Cubs? They were swept out of the postseason in the first round by Arizona last year, haven’t been to a World Series since 1945 and haven’t won one since 1908.

Chicago had a 2-0 lead on Mark DeRosa’s homer Wednesday night and then went flat against Derek Lowe and the Dodgers’ bullpen.

‘‘I felt like after we got that 2-0 lead, if we tack on a few more runs you can demoralize a team like that, just like they were able to do on us,’’ DeRosa said.

‘‘You have to go out and win tomorrow. You just have to relax, have fun. Z’s our horse.’’

After pitching a no-hitter against the Astros in Milwaukee, Zambrano struggled in his final two outings of the season. And the Cubs can’t afford another effort like the one they got from Dempster, who matched a career high with seven walks.

‘‘Let’s hope we get better,’’ Cubs manager Lou Piniella said.

Dodgers manager Joe Torre made his 13th straight postseason managerial appearance — the previous 12 were with the Yankees — and extended his record for postseason wins to 77 in a matchup with Piniella, another veteran skipper.

‘‘It does lot for our confidence,’’ Torre said. ‘‘We know how good Chicago is. We know how consistent they’ve been all year. And to have them get a lead and for us to just maintain our patience, it’s important.’’

Dempster walked the bases loaded in the fifth, and Loney delivered for the Dodgers.

After swinging and missing the first two pitches, he sent a 1-2 pitch over the wall in center for the grand slam that gave the Dodgers a 4-2 lead.

‘‘Invariably, when you keep putting people on, they’re going to score, and they scored there quickly with that grand slam,’’ Piniella said.

Sean Marshall gave up Ramirez’s solo shot in the seventh that made it 5-2. Casey Blake had an RBI single off Jeff Samardzija and Martin homered off Jason Marquis.

Dempster, 14-3 at Wrigley during the regular season, threw 109 pitches in just 4 2-3 innings, giving up four runs and four hits while matching a career high seven walks.

‘‘I sure put myself in a tough situation,’’ Dempster said.

DeRosa’s wish is that Dempster gets to pitch another game in the series, meaning the Cubs keep it going and bounce back.

‘‘I know there’s a lot of guys that are down right now,’’ DeRosa said. ‘‘But you’ve got to come back, win tomorrow and go from there. We’ve got to even this series.’’ Notes: Greg Maddux pitched the ninth for the Dodgers. The 355-game winner made a couple of relief appearances in the postseason for Atlanta in 1998 and 1999. Maddux, who started his career with the Cubs and had two stints with them, got a warm welcome during pregame introductions.