Girardi left at 13:29 of the second period during the Lightning's 5-2 win against the Red Wings at Little Caesar's Arena.
"He's doing much better than that looked," coach Jon Cooper said after the game. "I've been coaching at all levels for a long time, and that was one of the scariest things I've ever seen, but hopefully everything is going to be OK. He's just going to have a couple tests."
Girardi is in first season with the Lightning. He signed a two-year contract on July 1 after 11 seasons with the New York Rangers, who bought out the final three years of his contract on June 14.
Girardi, who had a goal and an assist on Sunday, has 11 points (eight goals, three assists) in 42 games this season. His 96 blocks rank tied for sixth in the NHL.
The Lightning (30-9-3) lead the NHL with 63 points and play the Carolina Hurricanes at Amalie Arena on Tuesday (7:30 p.m. ET; SUN, FS-CR, NHL.TV).
Following their game against the Calgary Flames on Thursday, the Lightning have six days off.
