Coach Ralph Krueger was unable to provide further details on the severity of the injury because Eichel is still being evaluated. According to Sportsnet's Elliotte Friedman, "there are rumblings Eichel could be out longer term" but there has been "no clarification at this time."
Eichel favoured his neck after being checked into the end boards by Casey Cizikas with about four minutes left in a 5-2 loss to the New York Islanders on Sunday.
The injury is the latest to affect Eichel this season. He missed two games two weeks ago with a lower-body injury, and also missed the first week of training camp with an upper-body injury.
Having topped 20 goals in each of his first five seasons, including a career-best 36 last year, Eichel has scored just twice in 21 games this season, and in the midst of a 13-game scoring drought. With 16 assists, he still leads Buffalo with 18 points.
The injury comes at a time when the Sabres are on an 0-6-1 skid, and 2-11-1 over their past 13 outings. With a league-low six wins, Buffalo is already in jeopardy of extending its playoff drought to an NHL-record matching 10th season.
The Sabres are missing starting goalie Linus Ullmark, who is at least two weeks away from returning from a lower-body injury. Buffalo's blue line has also been depleted with Jake McCabe out with a season-ending right knee injury, and Will Borgen expected to miss another month with a broken forearm.
The Sabres are also hampered by a constricted schedule as a result of the team's season being placed on pause for a two-week stretch last month following a COVID-19 outbreak that affected nine players, plus Krueger. Buffalo's game against Philadelphia is its 14th in 23 days.
Krueger placed the emphasis on focusing on facing the Flyers and not the bigger picture.
"This is all about attitude right now," Krueger said. "We've had a lot of adversity to deal with, but we're dealing with it in the same way we have with good times, as we continue to push for growth, we continue to push for an attitude that moves us forward, and we continue to push for working on these solutions together."