The short outing by Carlos Zambrano wasn't just the Cubs being careful. Zambrano is injured:

So it was a bit of a surprise when Cubs manager Lou Piniella revealed that Zambrano left because of arm problems. Zambrano will have his right arm examined Wednesday.

Any absence could affect the Cubs, who are trying to hold on to first place in the NL Central, not to mention the best record in the league. With starter Rich Harden being skipped for precautionary reasons this week, this is news the Cubs didn't need to hear.

"He told our pitching coach he wasn't feeling good," Piniella said. "It has to be in his arm. I just don't know. We'll let you know tomorrow when we find out."

The Cubs are a deep team with an offense that's capable of winning with a less talented staff. I doubt that injuries to both Zambrano and Harden would keep them out of the playoffs at this point. It does, however, lower their chances of getting to the World Series given the front-line starters of the DBacks, Brewers and Mets, should any of those teams earn a playoff berth.