The defenseman had been day to day for nearly two weeks but was downgraded Wednesday; he has missed five games and has not played since a 3-0 loss to the Minnesota Wild on March 7.
Defenseman Anton Stralman has also missed the past five games with a lower-body injury.
"(Defenseman) Jan Rutta's up here, and as long as Dan's out, we've got other guys filling in and filling the void, and he's done a really good job so far," Lightning coach Jon Cooper said. "Hopefully, we'll get Stralman back here soon and give us a little bit more depth. It's a pretty important position. It's good to have depth, and we've got it right now."
Girardi has 15 points (four goals, 11 assists) in 61 games this season. He has 263 points (56 goals, 207 assists) in 926 games in 13 NHL seasons with the New York Rangers and Lightning. He signed with Tampa Bay as a free agent July 1, 2017, following 11 seasons with New York.
The Lightning (56-13-4), who have clinched the Presidents' Trophy, Eastern Conference, Atlantic Division and home-ice advantage throughout the Stanley Cup Playoffs, have won five straight games and 17 of 19 (17-2-0).
NHL.com staff writer Tom Gulitti contributed to this report
