Yu Darvish, who hasn't pitched since May 20 because of elbow pain, threw a 33-pitch, two-inning simulated game Wednesday without issue.
Darvish is expected to throw another simulation, probably Sunday at Wrigley Field, before beginning a rehab assignment.
If he begins a rehab assignment by the end of next week, a return to the Chicago Cubs' rotation by early September is possible.
"You've got to treat it like spring training now," Joe Maddon said of getting Darvish stretched out again. "You don't want to push it too hard right now."