Gaustad was initially ruled out for the rest of the season after he sliced a tendon above his left ankle in the Sabres' 3-2 win over Ottawa on Feb. 7, but made a quicker recovery. He had missed 35 games, including nine in the playoffs.
Gaustad had nine goals and 13 assists in 54 regular-season games, providing a physical presence on a line with co-captain Chris Drury. He had four assists in 18 games in last year's playoffs, helping the Sabres reach the East finals before losing Game 7 to eventual champion Carolina.
With the best-of-seven series against New York tied at two, Buffalo also welcomed back forward Maxim Afinogenov, who returned after being a healthy scratch in a 2-1 loss in Game 4 at New York on Tuesday.
The additions led the Sabres to sit out rookie forward Drew Stafford, who had two goals and two assists in nine playoff games, and Daniel Paille, who played his first game this post-season Tuesday.