Johnson had just returned from the disabled list July 6 after missing time with back problems and was 7-for-35 since then. He was sharing time in center with Kosuke Fukudome.
In the first inning, Johnson singled to lead off against the Houston Astros to spark a six-run inning. He also made the last out of the first when he flied out to center. Johnson stayed in the game and was lifted for defensive purposes after the second inning.
After the game, Cubs manager Lou Piniella wasn't sure about Johnson's status.
"It really got sore on him and it just got progressively worse," Piniella said. "Hopefully, it's nothing serious, just a bruise."
Unfortunately for Johnson, it is serious. The Cubs were one of two Major League teams to begin the season without a player on the disabled list, but since May 4, they have had 13 players go on the DL 15 times.
Johnson will be sidelined with catcher Geovany Soto -- who is rehabbing in Mesa, Ariz., from a left oblique strain -- and pitcher Ted Lilly, who has inflammation in his left shoulder. Infielder Aaron Miles (hyperextended elbow) also is on the DL.
The Cubs will make a roster move on Thursday and could recall outfielder Sam Fuld, who batted .368 in 12 games with the Major League team in a previous stint.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.