Even after the experience Holt went through in 2014, it took him a few days to realize he had a concussion after making a dive at second base against Oakland on May 10.
"I went in and I played second base when were up in one of those games and I made a dive and I hit the ground pretty hard," said Holt. "I didn't hit my head, but I remember getting up from the dive and I knew that I hit the ground pretty hard. I went home that night and was pretty dizzy at the house, dizzy and light-headed.
"I came in the next day and told the trainers and thought I had a bit of a whiplash, so we're treating my neck. And like I said, once my neck started feeling better, but I was still getting dizzy and light-headed, I knew something was probably going on."
Holt hopes he is symptom-free when the seven-day disabled list stint ends on Wednesday, but he knows there are no guarantees.
"I've been asked that question by friends and family and everything like that," said Holt. "But yeah, you really don't know. Just kind of take it day by day and see how you feel every day you wake up, so we're going to make sure that it's right before I get going again."
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.