Ruff - speaking to reporters Sunday as the team prepared for Monday night's Game 6 of the Eastern Conference quarterfinals series against Boston -- said Vanek has taken a step forward in his drills as he recovers from an ankle sprain sustained in Game 2's loss, NHL.com reported.
Ruff said there is a possibility the Sabres' leading scorer could suffer a setback as he engages in more physical contact.
"We're going to try to get him involved in some battle drills, which he hasn't been involved in," Ruff told the Web site. "We'll get a pretty good idea of where he's at. I think you run the risk when you start getting him involved physically that you could set it back. We don't know."
Vanek was hurt when he was checked from behind by the Bruins' Johnny Boychuk. Both slid into the endboards and Vanek limped back to the Buffalo bench. Boston went on to win 5-3.
The Bruins hold a 3-2 series advantage.