Eichel fell backward as he was checked by Bruins defenseman Matt Grzelcyk along the boards behind the Bruins' net. He appeared to be favoring his right knee as he left the ice.
Eichel is expected to have an MRI on Sunday, according to the Buffalo News.
"He got tangled up in the corner, but we'll know more [Sunday] when he sees our doctor," Sabres coach Phil Housley said.
Eichel, the No. 2 overall pick in the 2015 draft, leads the Sabres with 22 goals and 53 points. He missed the first 21 games of the 2016-17 season because of a sprained ankle.
The Associated Press contributed to this report.