PHOENIX -- Reliever J.J. Putz is working toward getting back into the D-backs' bullpen.
The 37-year-old right-hander hasn't pitched since May 3 due to a forearm injury, but he will throw a simulated game on Friday.
"We'll just go from there," Putz said.
Putz said his arm feels "great" and that he was able to long toss without any pain.
"[Trainer Ken Crenshaw] put me on a pretty tough shoulder and forearm workout the last three weeks, two days down and one day off," Putz said. "It feels stronger, but until you get up there and face hitters, you don't really know."
Before the injury, Putz had pitched in 13 games for the D-backs -- 10 innings - while giving up six earned runs and walking six with 12 strikeouts.
Putz has been successful in the past. In his four years with the D-backs, he has a 2.64 ERA in 156 2/3 innings.
Marshall, who was called up when Putz was placed on the disabled list, has impressed early in his career.
The 6-foot-2 right-hander has given up only one earned run -- a go-ahead home run to Padres first baseman Tommy Medica in Tuesday's 4-3 loss to the Padres -- since making his debut on May 6. In 9 2/3 innings, he has 10 strikeouts.
"Marshall's been great for us," manager Kirk Gibson said.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. Adam Lichtenstein is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.