The center is expected to be ready for next season.
"Very, very difficult," Sabres coach Don Granato said Wednesday. "Knowing as a person, his commitment, his character, and he's playing through it. And it's not something you want exposed, obviously, because it's such a competitive environment, so that's information you don't want the opponents to have, obviously, for his safety. … It's a bummer. It is. You just hope for him to feel better every day and improve every day, and that's in essence what you think of and how you think about it."
Eichel scored 18 points (two goals, 16 assists) in 21 games and last played March 7, a 5-2 loss to the New York Islanders. The Buffalo captain was reevaluated after not playing in a 5-4 shootout loss to the Philadelphia Flyers two days later and was expected to be out at least 7-10 days.
Granato said he was not sure if Eichel would need surgery.
"Our medical team, you know, you hand it off as a coach to them and the doctors, between our trainers, our doctors and (general manager) Kevyn [Adams]," Granato said. "So any information regarding that, I wouldn't have, honestly. I just stay out of it. I communicate with Jack, but even when I talk to Jack, I don't talk about the injury. He has enough people talking to him about the injury, so it's not my role."
Adams said Thursday that Eichel will continue to rehab the injury and be evaluated in early May but did not say whether he would need surgery.
"The course of treatment was to rehab it and give it some time to see if the disk had moved back to where the doctors were comfortable, and then the hope was that he could jump back in and play," Adams said. "That was done last week, and though there were slight improvements, there still wasn't a comfort from anyone that it was the right time to jump back into the lineup.
"I think the key here is that we all want the same thing for Jack, and Jack included. We all want him back on the ice, [one] hundred percent healthy, and we all feel that will happen at the start of training camp next year. But next steps will be next steps in a few more weeks, where we go from here."
Eichel missed two games with a lower-body injury Feb. 25 and Feb. 27. The two goals scored in 21 games were the fewest to start his six-season NHL career.
The Sabres lost 18 straight games (0-15-3) from Feb. 23- March 29, including the final 11 without Eichel.
"Yeah, it's tough," Buffalo forward Sam Reinhart said. "I mean, it's always tough missing time. You know, no one wants to go through a stretch like this, watching games, so you just hope he recovers and comes back better."
Selected by Buffalo with the No. 2 pick in the 2015 NHL Draft, Eichel has scored 355 points (139 goals, 216 assists) in 375 games. He scored at least 24 goals in each of his first five NHL seasons, including a career-high 36 last season.
The Sabres (10-25-7) are last in the NHL standings. They visit the Washington Capitals on Thursday (7 p.m. ET; NBCSWA, MSG-B, NHL.TV).
NHL.com columnist Nicholas J. Cotsonika contributed to this report
