Denard Span. (AP Photo/David Goldman)

Denard Span flew back to Washington on Wednesday ahead of the Nationals to be evaluated by a doctor there. The outfielder suffered a mild concussion on Friday and, along with feeling better, has ramped up his physical activity. He scored higher than his baseline score on his concussion test on Tuesday.

If he passes his evaluation on Wednesday, he could begin his rehab assignment as soon as Thursday, Manager Matt Williams said. He would be slated to get three at-bats in his first rehab game on Thursday. He would then get four at-bats in a rehab game on Friday. Barring inclement weather, Williams said Span would likely play at a local minor league affiliate.

If all goes well, Span could rejoin the Nationals on Saturday, the first day he eligible to come off the seven-day concussion disabled list. “We’ll make sure that he’s good to go and get him back as soon as we can,” Williams said. Span and the Nationals want to be cautious because the outfielder suffered a concussion that limited him to only 70 games in 2011.

Span suffered the most recent concussion on Friday when he collided with Dan Uggla rounding first base in the eighth inning.

>>> Doug Fister, who is rehabbing from an lat muscle strain, left the Nationals on Wednesday for extended spring training at the team’s facility in Viera. The right-hander will resume a five-day throwing schedule on Thursday, starting with two innings in extended spring training, Williams said. He would then throw three innings.

If there are no issues after that, Fister would then begin a minor league rehab assignment and make starts of four and five innings, Williams said.

“That’s the tentative plan,” Williams said. “It’s not writen in stone because you don’t know how he’s going to feel. It may even turn out to be bigger than that depending on how he goes:

Fister, the Nationals’ prized offseason acquisition, strained his lat pitching in a minor league spring training game March 27, after he had spent most of spring training recovering from elbow inflammation. He threw his first bullpen since the injury on Friday in Atlanta and then 50-pitch bullpen session with all of his pitches on Monday in Miami. In between his extended spring training starts, Williams said Fister may rejoin the Nationals to keep up with his rehab.

If Fister stays on his five-day pitching schedule and is ready to return after the next four starts, the soonest he could pitch in the major leagues is May 7.

>>> Scott Hairston (oblique) is continuing the rehab work on his side but has yet to swing a bat since straining his oblique, Williams said.

>>> Kevin Frandsen was dealing with back spams in his pinch hit at-bat in the ninth inning of Tuesday’s loss, Williams said. The utility man is available on Wednesday.