PHILADELPHIA — In a season seemingly filled with adversity, the Buffalo Sabres were delivered another significant blow Tuesday with the news that an upper-body injury would sideline center Jack Eichel for at least one week. . . Eichel was not available to play for the Sabres on Tuesday night against the Philadelphia Flyers in Wells Fargo Center. Coach Ralph Krueger would not disclose how the injury occurred or if this could keep the 24-year-old captain out of the lineup long term. . . Eichel was grabbing at his neck and in discomfort on the teams bench after he was pushed against the glass in the third period of a 5-2 loss to the New York Islanders on Sunday. Its tough, said Sabres forward Casey Mittelstadt. Obviously, hes our leader, its been a tough stretch for us. . . Eichel is the Sabres top-line center, the triggerman on a power play that entered Tuesday ranked third in the NHL and one of the top young stars in the National Hockey League. . . Much has been made about Eichels lack of scoring during his sixth NHL season. The former second overall draft pick has two goals with 16 assists for 18 points in 21 games. Eichel missed the start of training camp with an upper-body injury and a lower-body injury kept him out of the lineup for consecutive games last month. . . However, Eichel has evolved into an outstanding, responsible two-way forward who can apply pressure on opponents defensively. . . Jack not playing Tuesday is certainly a big hole and a big loss on both ends of the rink, said Krueger. Hes the quarterback on the power play. He was really putting a lot of pressure on the puck defensively like you said, neutralizing a lot of transition already in the neutral zone with his speed and angling and we were able to push teams back into their own end. . . A viable Hart Trophy candidate with a career-high 36 goals last season, Eichel has gone 13 consecutive games without a goal and is shooting a career-low 3. 3%. He is the latest Sabres player to endure bad injury luck, joining defenseman Jake McCabe and winger Zemgus Girgensons, both of whom are out for the season. . . Although the Sabres have improved depth at center, it will be difficult to replace Eichels production and workload. He scored at least 24 goals in each of his five previous seasons, establishing career highs in 2018-19 and 2019-20. Eichel is averaging 20. 30 of ice time per game, almost two fewer minutes than last season, and ranks fifth on the team in 5-on-5 time on ice. Its about the group all chipping in on this one, said Krueger. Its everybody adding value wherever Eichels ice time of 20-plus minutes is usually spent. We do have more depth this year than we had last year to be able to fill a hole like this and, yeah, Im looking forward to seeing guys step up to the plate for the minutes that Jack is going to be missing it. . . Ullmark update. . Goalie Linus Ullmark lower-body injury is still a few weeks away from returning to the Sabres lineup, Krueger said. . . Krueger, who would not provide specifics about Ullmarks rehab, told the media that the Sabres are being cautious with the 27-year-olds recovery. Ullmark is 5-4-2 this season with a 2. 44 goals-against average and team-best . 919 save percentage. He suffered the injury in the first period of a 4-3 overtime loss to the New Jersey Devils on Feb. 25. . . Linus, hes still in a very, very careful rehab, said Krueger. Well see on Wednesday where hes at. Were just going step by step, but hes definitely still a few weeks away from any intensive puck play or on the ice with full equipment. But rehab teams doing a good job on him and were just being careful with the type of injury he has.