Drouin got up slowly and exited to the locker room after he was pushed down by T.J. Oshie 3:48 into the second period. Drouin returned without missing a shift but left again with 3:29 remaining. Coburn left after taking a hit from Tom Wilson in front of the Lightning net 7:25 into the period.
Lightning defenseman Victor Hedman spent the final 9:28 of the second period in the locker room but returned for the start of the third period and finished the game. Hedman said he "took a bad hit."
"I was able to come back and I was happy to do that," Hedman said. "You never want to miss time. When you get hurt, you feel like you want to be out there, and even though you're down (3-0 after two periods) you still want to be out there and help your teammates."
Cooper said having Drouin, Coburn and Hedman leave the game in the second period "didn't help either."
"Hedman was, fortunately, able to come back. The other two weren't," Cooper said. "But it's tough. It's been the tale of our December, guys getting hurt, so you were just hoping nobody else was going to."
The Lightning, who next play Wednesday against the Montreal Canadiens, have lost 77 man games to injury this season. That includes the past 18 games without captain Steven Stamkos, who has been sidelined since Nov. 15 because of a lateral meniscus tear. Goaltender Ben Bishop is expected to miss 3-4 weeks with a lower-body injury he sustained against the Detroit Red Wings on Tuesday.
The Lightning also are missing right wing Nikita Kucherov (lower body), right wing Ryan Callahan (lower body), left wing Ondrej Palat (undisclosed) and center Cedric Paquette (lower body).
Drouin, who missed seven games in November with an upper-body injury, has seven goals and six assists in 10 games this month, including two goals and an assist in a 5-2 win against the St. Louis Blues on Thursday.
