"This is a very unique one," said Red Sox manager John Farrell. "We talked a lot about his form of a concussion and felt like the best way for him to get back to being capable with us is to push forward and stress the intensity, the level of play, because the symptoms aren't going to go away just by sitting around. This is a matter of getting active and being aggressive with it so hopefully everything calibrates within his system, and that's the recommendation of the medical staff."
With two other left fielders on the disabled list, the Red Sox need Holt, but they know they can't rush a player back from a concussion.
"He had a good day yesterday but just didn't feel like he's ready to take that next step," said Farrell. "We have to respect that. He'll get a full number of at-bats tomorrow and Wednesday before we get back home."
Farrell was asked if Holt was having vision problems.
"No, not vision," said Farrell. "As I understand it, there is a slight disoriented feeling that we're working through."
• Reliever Brandon Workman, who is on the comeback trail from Tommy John surgery, drove up from Fort Myers, Fla., and threw a bullpen session in front of the Red Sox. Workman has been throwing in games in Florida and the hope is that he'll start an official rehab at Class A Lowell in the near future. Perhaps Workman can give Boston's bullpen a lift later in the season.
"That's been my goal from the time I got surgery through today," said Workman. "I've been working, trying to get myself in a position where I can come back sometime this year and be a contributing part."
• Shortstop Xander Bogaerts, who admitted he was tired after Sunday's game, is likely to get a day off on Tuesday.
• Catcher Ryan Hanigan (neck strain) will catch nine innings on both Tuesday and Wednesday for Triple-A Pawtucket and could rejoin the Red Sox by this weekend.
Ian Browne has covered the Red Sox for MLB.com since 2002. Follow him on Twitter @IanMBrowne and Facebook. This story was not subject to the approval of Major League Baseball or its clubs.