"Just all the blood and everything, whenever you see that blood, you get a little weary of what's happening and stuff," Carlson said. "I'm sure I lost a little bit that day, but they do say you get a lot of blood to the brain, so that's a good thing for me in the moment."
Capitals coach Peter Laviolette was among those to check in with Carlson later that night and the following day.
"There's no question it was scary," Laviolette said. "It was scary for 24 hours there. So it was really good to hear the prognosis and to know that John was going to be OK and that in time everything would be back to normal. It's a dangerous game out there at times. It's fast. It's physical. The hits, the puck flies around at 100 miles an hour, there's a lot of things that can go on and you always want to make sure the player are protected. But there's things that pop up sometimes that scare you. They're dangerous and they scare you."
Carlson said he was fortunate he did not have any concussion symptoms, but it took time for the pain in his head to subside, and he addressed the possibility of being a bit apprehensive about certain game situations.
"For sure, you hear a puck coming around the glass or something and you don't quite know where it is," he said, "they're nerve-wracking things regardless of anything and you can't discount that. But, yeah ... you have to be in it to either, a, know how you feel or, b, kind of return to normal. So that's where I'm at."
Carlson was asked if he ever doubted he would return this season.
"Yeah. I guess anyone could have thought that," he said, "and I'm sure at some point I had, but like most everyone else in here, I would imagine we're pretty goal-oriented people and when you have a target, a goal, a conversation, you've got to have something to work to and, obviously, it's not always that simple. It doesn't always go as planned. Some parts are harder, some parts are easier and whatever it is, I think we all have goals in here and certainly I had a goal to come back if it was safely possible, and that's where I'm at."
The Capitals (33-31-8) trail the Pittsburgh Penguins by six points for the second wild card into the Stanley Cup Playoffs from the Eastern Conference with 10 games remaining.
Carlson's absence has created an unfillable void for Washington. Selected by the Capitals with the No. 27 pick in the 2008 NHL Draft, he is their all-time leader among defensemen with 614 points (140 goals, 474 assists) in 917 regular-season games over 14 NHL seasons.
Carlson has 21 points (eight goals, 13 assists) and was leading Washington by averaging 23:24 in ice time in 30 games this season before he was injured. The Capitals were 19-13-4 the day he was injured and have gone 14-18-4 since.
"Just a really important piece to our team," Laviolette said. "We felt it the minute he left. It's really good to get him back. He's worked hard to put himself in the position to be in shape and ready to go, healthy, and we're excited to have him back."
Laviolette said the Capitals won't hold Carlson back.
"We have a lot of really good doctors and a really good training staff and we would not put somebody back in there that was not cleared by the doctors and able to handle themselves and take care of themselves out on the ice," Laviolette said. "So I think that there's situations that happen that you do sit there and say, 'OK, we're not moving forward with this player.' However, there's times that come up where everything is cleared, the player is healthy, he's in shape, he's able to do everything he needs to do."
Goalie Darcy Kuemper will also return for Washington on Thursday after missing two games with an upper-body injury. He last played on Friday, when he allowed four goals on 21 shots in a 5-2 loss to the St. Louis Blues.
