The Devils said that Kovalchuk is day to day. He has three goals in eight playoff games. He led the Devils with 37 goals and 83 points this season.
"We left Ilya Kovalchuk back in New Jersey and he will not be in the lineup and the reason is a lower-body injury and that's all we will say," Devils general manager Lou Lamoriello said. "He is day to day. We'll have no other further comments on Ilya's situation."
The Devils say Kovalchuk was injured in the first-round series against Florida. The Devils won Games 6 and 7 of that series in overtime, to set up this matchup with Philadelphia. It was Kovalchuk's first series win of his career.
The Flyers lead the Devils 1-0 after a 4-3 overtime win in Game 1 Sunday. Kovalchuk was a minus-2 and had no shots on goal in the loss.
It is expected that defenseman Peter Harrold, who has three points and five shots on goal this postseason, will be moved up to a forward position to replace Kovalchuk's spot in Game 2. He will play right wing.
That would allow room for rookie defenseman Adam Larsson to be activated. Larsson was a first-round pick last year, and is just 19 years old. He had two goals and 18 points in his first NHL season, but has not played a playoff game yet.
The Devils also recalled Tim Sestito from AHL Albany.
Information from The Associated Press was used in this report.