Malkin, who had two assists in a win Wednesday against Tampa Bay, has five goals in his past 29 games.
“I’m disappointed for him because he had a great game [Wednesday] ,” Sullivan said. “We think that was a game he could really build on, but we’re hopeful this is a short-term thing. Certainly the fact that he had a strong game as he did the other night is encouraging, and we’re looking forward to getting him back in our lineup.”
The Associated Press contributed to this report.