CINCINNATI | Right-hander Carlos Zambrano was upbeat Friday about his chances of returning to the Cubs' rotation in a week, optimistic that an anti-inflammatory injection and rest will be enough to heal his aching shoulder.

Zambrano rejoined the team for the start of a series against the Cincinnati Reds one day after he got a medical test that detected inflammation in his right shoulder. He had to rest for two days after getting an injection, and hoped to be back in the rotation next weekend.

"I've been worried," he said. "But I was OK. Thank God it wasn't serious."

Zambrano's sore shoulder sent a shiver through Cubs fans waiting for something to go wrong in their dash to the postseason. The NL Central leaders had lost a season-high five in a row heading into the weekend series, and their rotation seemed to be falling apart.

Besides Zambrano's sore shoulder, Rich Harden has discomfort in his arm that will cause him to skip his scheduled start on Sunday. Sean Marshall will face the Reds instead.

The Cubs are accustomed to tough times. This is the 100th anniversary season of their last World Series win. They won the division last season, clinching during a visit to Cincinnati, but failed to make it past the first round of the playoffs.

Even the trip to the ballpark is becoming an odyssey these days.

Manager Lou Piniella and first base coach Matt Sinatro decided to drive to Cincinnati from Chicago on Friday. With Sinatro behind the wheel and directions at hand from a Google search, the two set out at 8 a.m. and headed across the northern part of Indiana and Ohio.

With Piniella catching up on sleep, the pair kept going past the turnoff for Interstate 75 that would take them south to Cincinnati. They kept going east and were closing in on the Pennsylvania border when they realized something was badly wrong.

"We stopped at one of the (gas) stations along the way, and I bought a map to see exactly where we were," Piniella said. "And we realized we were in the opposite end of the state.

"It wasn't his fault. I was in the car also. I probably shouldn't have taken the nap."