The Chicago Cubs scratched left-handed pitcher Ted Lilly from his Saturday start because of soreness in his left shoulder.
Lilly will go for tests Friday at Northwestern Hospital for an arthrogram to determine the extent of the injury or soreness.
In addition, Lilly has been suffering with a left knee problem the past three weeks.
The Cubs open a three-game series against the Cincinnati Reds on Friday.
Kevin Hart will fill in for Lilly on Saturday, according to a team source.
Lilly, Chicago's only All-Star this season, is 9-7 with a 3.59 ERA. He is coming off his worst start of the season, having allowed nine runs in four innings in Monday's 10-1 loss at Philadelphia.
Bruce Levine covers baseball for ESPNChicago.com. Information from The Associated Press was used in this report.