First baseman Brandon Belt's errant throw during batting practice at Citi Field last week struck Blanco in the head, causing him to miss the past four games. Belt missed nearly two weeks last season with a concussion, which oddly happened in the same way as Blanco's.
The Giants are also without right fielder Hunter Pence, who was placed on the disabled list June 11 (retroactive to June 3), making Blanco's absence even tougher on manager Bruce Bochy.
"It does make it tougher when you have two outfielders down," Bochy said. "It goes to show you how valuable Gregor Blanco is."
Blanco, who was hitting .278 with one home run and seven RBIs in 48 games before the injury, can play all three outfield positions and gives Bochy more flexibility when he is available.
Blanco rode a stationary bike Saturday, but Bochy said he felt some dizziness after his workout. Blanco said he hopes to swing a bat Monday.
"I'm hoping he does, too," Bochy said before the Giants' series finale Sunday vs. the D-backs. "It's hard to say with these concussions. I'm hoping he makes a big turnaround today, though."
With Belt and catcher Hector Sanchez both suffering from concussions last year, the Giants' medical staff has dealt with issues like this in the past. The team will continue to err on the side of caution.
"With our experience in what we had last year with [Belt], I'm sure they are going to be more careful," Bochy said. "I think we're really going to be on the cautious side here and make sure he's ready before we activate him."
Oliver Macklin is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.