Chen, who is at the team's spring facility in Sarasota, Fla., threw a 45-pitch bullpen session on Monday and will throw a simulated gamed on Thursday. Showalter said Chen, who has now thrown off a full mound twice, would have another simulated game after that.
Chen was placed on the disabled list on May 14 (retroactive to May 13) and went 3-3 with a 3.04 ERA in his first eight starts.
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.