(Alex Brandon /AP)

Having played all season with several key pieces on the disabled list, the Nationals will start to get some of their injured players back this week.

Right-hander Doug Fister, the offseason trade acquisition who has missed all season with a right lat strain, will debut Friday in Oakland, Manager Matt Williams said. The Nationals had originally planned for Fister to start Wednesday, but they moved him back because they did not want to give Stephen Strasburg extra rest after he threw only 83 pitches Friday night. Strasburg will start Wednesday on regular rest.

As chance would have it, Fister faced the A’s last year in the ALDS as a member of the Tigers. In an 8-6 Detroit win, Fister allowed three runs in six innings on seven hits and a walk, with just one strikeout.

The Nationals have yet to determine their starter for Tuesday, Williams said. They would prefer for Ross Detwiler to make the start, but Williams does not want to limit his ability to use Detwiler on Monday night against the Dodgers. If Detwiler does not pitch, the Nationals would call up Blake Treinen to make the start.

The Nationals could get their first reinforcement off the disabled list Monday, when they start a series at Nationals Park against the Dodgers. Outfielder Scott Hairston, the Nationals’ primary pinch hitter off the bench, went 0 for 4 with a strikeout Sunday at Class AAA Syracuse, playing all nine innings.

The Nationals placed Hairston on the disabled list with an oblique strain April 6. Barring any setback, Hairston will rejoin the Nationals on Monday. Outfielder Steven Souza Jr. will likely be optioned to Syracuse to make room on the roster.

Meanwhile, catcher Wilson Ramos took another step closer to his first major league action since opening day, when he broke his hamate bone. Serving as the designated hitter at Class A Hagerstown, Ramos went 2 for 3 with a home run and a walk. Including at-bats in extended spring training, Ramos has blasted three homers in his rehab, an excellent sign — many players who suffered hamate injuries lose power upon their return. Ramos should be back with the Nationals sometime this week.