Randy Wells was in the Cubs' bullpen on Tuesday but would only be used in an emergency, manager Dale Sveum said.
Wells, who has made two starts subbing for Ryan Dempster, including Saturday in Philadelphia, threw a bullpen session on Monday. He will be more available Wednesday. Dempster, sidelined with a strained right quad, is expected to be activated from the disabled list Thursday to start the series finale against the Reds.
Kerry Wood, who has not pitched since April 13 because of fatigue in his right shoulder, remained on track to come off the disabled list Thursday. Said Sveum: "Everything's good."
Starlin Castro and Tony Campana are the first Cubs duo to have at least seven stolen bases in the first month since stolen-base records were first kept in 1921. Castro leads the Major Leagues with 10 steals, and Campana has seven.
The Cubs have 20 stolen bases in 23 games this year. They did not record their 20th steal last season until June 16, the 68th game.