Stralman hasn't played since sustaining the injury in a regular-season game against the Islanders on March 25 when he and Islanders forward Anders Lee were battling for position in front of the Lightning net.
Stralman has participated in the optional morning skates prior to the two games in New York.
The Lightning lead the best-of-7 series 2-1; Game 5 is at Amalie Arena on Sunday (3 p.m. ET; NBC, SN, TVA Sports).
Cooper, asked when to expect Stralman's return, said, "That one's a little baffling to me. Way back when this series was starting, I was hoping this game or maybe the next one he could come back in. I'm a coach, not a doctor. I was way off on that one.
"Is there a chance he can come back? I guess. But I haven't been told. Is he going to be ready for this one? He's not ready to go tonight. It'd be doubtful he'll be there for Sunday."
Stralman, 29, had nine goals, 25 assists and a plus-16 rating in 73 games during the regular season.
Lightning captain Steven Stamkos (vascular surgery) skated Friday in a non-contact jersey but did not speak with reporters afterward. Cooper did not provide any update on the center's status.
