The second-overall pick in 2015 suffered a high ankle sprain the day before the Sabres’ season opener.
The news comes just one day after head coach Dan Bylsma announced that Eichel was “progressing nicely” and going to see a doctor.
“He’s been working out at another level the last four or five days and hopefully he continues to progress to get to the ice soon,” Bylsma told reporters after the morning skate on Wednesday.
Eichel’s injury occurred just over four weeks ago, and a high ankle sprains typically sidelines athletes between six to eight weeks.
He has missed all 13 games this season, and, if he is out for another four weeks, he will miss an additional 13 games.
The 20-year-old played in 81 games for the Sabres last year and recorded 24 goals and 56 points.