Gio Gonzalez could be looking at a June 11 return to the Nationals. (Alex Brandon/Associated Press)

Nationals left-hander Gio Gonzalez threw roughly 35 pitches in a bullpen session Thursday, and if his inflamed left shoulder does not flare up, the Nationals have set a path for his return to the Nationals’ rotation.

Gonzalez is scheduled to throw 50 pitches in a simulated game Sunday morning at Nationals Park. Assuming that session goes well, Gonzalez will pitch five or six innings at a minor league affiliate five days later, Manager Matt Williams said.

“That’s the tentative plan right now,” Williams said.

On that schedule, Gonzalez would be on pace to make his return from the disabled list June 11 in San Francisco against the Giants. The Nationals placed Gonzalez on the disabled list May 18, the day after he suffered through a punishing three-inning start.

Until Gonzalez returns, right-handed rookie Blake Treinen will take his place in the rotation. Treinen’s scheduled became muddled when the Nationals skipped him after his start was rained out Tuesday night.

Williams said Treinen will be available to pitch out of the bullpen for the next three days. If Treinen does not get into a game, then he would throw a “heavy” bullpen session or a simulated game Tuesday, Williams said. That would set up Treinen to start June 8 in San Diego. The Nationals can be flexible with their rotation because of an off day Monday.

“We just don’t know, because we don’t know how the games are going to go,” Williams said.

Treinen warmed up to pitch in mop-up duty Wednesday night. But after the Nationals erased a 4-0 deficit, Williams sat him down and used the regular back end of his bullpen instead.