Kovalchuk did not make the trip to Philadelphia for Tuesday's game because of a lower back injury suffered in the opening round against the Florida Panthers.
Coach Peter DeBoer said the right wing was feeling better on Wednesday, and Kovalchuk said on Thursday morning that he expected to play.
Kovalchuk had 37 goals in the regular season. He had three in the first eight games of the playoffs.
Rookie defenseman Adam Larsson, who replaced Kovalchuk in the lineup for Game 2, remained after scoring in the 4-1 win. Instead, defenseman Peter Harrold was a healthy scratch for the first time in the playoffs. He has four points in nine postseason games.