Hughes, who just made his second All-Star Game appearance over the weekend, had two goals in three points Monday in the Devils' 5-4 overtime win against the Vancouver Canucks. He set up Jesper Bratt to score the game-winning overtime goal while also leading all Devils forwards with 21:44 in ice time.
Hughes, 21, practiced Wednesday but did not finish the session, which created some questions about his availability going forward. That culminated with Ruff saying Hughes' absence would start Thursday against the Seattle Kraken.
"He's a young guy; that will help him," Ruff told reporters after morning skate. "I think it's going to be on the shorter end of it."
Ruff said forward Alexander Holtz will go into the lineup, with Hughes' injury creating an opening. The 21-year-old Holtz, who was the No. 7 pick of the 2020 NHL draft, has four points in 18 games and has not played this season since Jan. 7, when he logged 8:55 seconds in a 4-3 overtime win against the New York Rangers. With Holtz being a winger, the expectation is that Dawson Mercer will move to center after playing on the wing. Mercer, who was the No. 20 pick of the 2020 draft, is fifth on the Devils with 29 points while also scoring 11 goals.
Being without Hughes leaves the Devils without their Hart Trophy candidate, who is enjoying his strongest season since going No. 1 in 2019. Hughes' breakout campaign has led to him scoring 35 goals and 67 points through 50 games. He was projected to finish with what would have been his first 50-50 season with 57 goals and 52 assists for what also would have been his first 100-point campaign over an 82-game schedule. He leads the Devils in goals and points while being second behind defenseman Dougie Hamilton in assists.
Even with the injury, Hughes' 67 points are the most of his career, with his previous personal best in a season coming in 2021-22 when he finished with 26 goals and 56 points in 49 games.
The Devils, who entered Thursday second in the Metropolitan Division, will also be without defenseman Brendan Smith who is day-to-day with a lower-body injury.