"I doubt if he'll play the rest of the season," Ruff said.
The Stars already are without defensemen John Klingberg and Jordie Benn and will play two of their division rivals later this week.
The Stars host the Chicago Blackhawks on Friday and the St. Louis Blues on Saturday. The three teams are separated by three points atop the Central Division standings, with the Blackhawks visiting the Blues on Wednesday (8 p.m. ET; NBCSN, TVA Sports).
Klingberg missed his second straight game Tuesday and is day-to-day with a lower-body injury, but Ruff said he hasn't begun skating yet. Benn has missed the past three games with a lower-body injury and was expected to miss 1-2 weeks from the time of his injury on March 1.
The injuries to Klingberg and Benn pushed Jamie Oleksiak and Patrik Nemeth into the Stars lineup and also increased their reliance on new acquisition Kris Russell and Alex Goligoski on the top pairing.
Russell played 27:45 on Tuesday and Goligoski logged a game-high 29:15. Oleksiak and Nemeth played 14:00 and 15:16 respectively.
"I thought Oleksiak and Nemeth gave us some good ice time under the gun," Ruff said. "They're going to need to give us even more."