The 22-year-old forward tore a meniscus in his left knee during the Blackhawks' five-game loss to the Vegas Golden Knights in the best-of-7 Western Conference First Round.
"[Nylander] initially rested and trained conservatively," Blackhawks team physician Dr. Michael Terry said. "Unfortunately, his symptoms came back when he started to skate."
The NHL and NHL Players' Association formally reached an agreement Sunday to play a 56-game regular season starting Jan. 13, 2021, and ending May 8. The 2020-21 season has been delayed due to continuing concerns surrounding the coronavirus.
According to the timeline provided by the Blackhawks, Nylander is expected to be out until at least the third week of April.
Nylander scored an NHL career-high 26 points (10 goals, 16 assists) in 65 games for Chicago last season. He did not score a point in eight postseason games.
Selected by the Buffalo Sabres with the No. 8 pick in the 2016 NHL Draft, Nylander has scored 32 points (13 goals, 19 assists) in 84 games over four seasons in the League.
