(AP Photo/Alex Brandon)

Nationals right-hander Doug Fister pitched two innings Thursday afternoon in Viera, Fla. and, barring another setback, is scheduled to make his Washington debut in roughly three weeks, Manager Matt Williams said.

Fister, the Nationals’ prized offseason acquisition, recovered from early-spring elbow inflammation in time for the regular season, only to suffer a lat strain during his final spring training start. Fister made his biggest step yet in an extended spring training start, throwing 28 pitches over two innings.

“No issues,” Williams said. “He felt good about it. Reports are his first inning was better than his second inning, which is a good sign.”

Fister will begin a once-every-five-days schedule, Williams said, until he builds enough arm strength to join the Nationals’ rotation. Five days from Thursday, according to the Nationals’ plan, Fister will throw 45 pitches over three innings in another extended spring training start. Five days after that, Fister will pitch at a minor league affiliate. Five days after that, Fister will make a final rehab start.

“We’ve got to build him like we would build him in spring,” Williams said. “I think he’s a little bit ahead of the game in that regard. Certainly we’d like him to get five innings somewhere at least, to make sure he can up that pitch count.”

The Nationals, Williams said, have not cemented a specific day for Fister to make his season debut. Going by their ideal schedule, Fister would make his return May 7 against the Dodgers at Nationals Park. The Nationals have an off day the following day, which allows them extra flexibility if needed.

“We’re looking at that time period, somewhere in there,” Williams said. “We can push him back a day, too, if he’s sore at all or anything like that. So, 20ish days, if all goes well.”

The Nationals acquired Fister, 30, this winter from the Detroit Tigers for infielder Steve Lombardozzi, reliever Ian Krol and pitching prospect Robbie Ray.

Last year, including the playoffs, Fister pitched 220 2/3 innings.