BUFFALO, N.Y. -- The Buffalo Sabres will be leaning on their fourth-, fifth- and even sixth-string goalies for potentially the remainder of the season with Linus Ullmark listed as week to week with a lower-body injury.

Interim coach Don Granato provided the update on Ullmark on Friday, saying the timetable for his return is "touchy" because the Sabres only have three weeks left in their season. The Sabres sit last in the NHL standings and are all but mathematically out of contention.

Ullmark has missed one game after being shaken up in the opening minutes of a 3-2 shootout loss at Boston on Tuesday. The third-year starter has a 9-6-3 record, and went 4-2-1 in seven games upon returning after missing 15 games with a lower-body injury.

Backup goalie Carter Hutton's status remains cloudy, having missed 13 games with a lower-body injury. Though Hutton has resumed skating on an individual basis, Granato said there is no timetable yet for his return.

The injuries leave the Sabres preparing to call up top minor-league prospect Ukko-Pekka Luukkonen to make his NHL debut. The timetable for that is uncertain with Luukkonen recovering from an injury he sustained earlier this week.

Granato said the team will know more after Luukkonen practices with the AHL Rochester Americans.

The Sabres are currently left with two healthy goalies - Dustin Tokarski and minor league journeyman Michael Houser -- in preparing to host the Pittsburgh Penguins on Saturday and Sunday.

Tokarski stopped 27 shots in a 5-2 win at Washington on Thursday to improve to 1-4-2 this season. It was his first win since stopping 25 shots for Montreal in a 3-1 victory over Ottawa on Dec. 12, 2015.

Howser has never appeared in an NHL game, and was signed last month after Buffalo agreed to trade goalie Jonas Johansson to Colorado.

Veteran forward Kyle Okposo's status is also uncertain. Granato said the team is awaiting test results after Okposo was struck in the face by a puck against Washington.

The latest injuries come the same week in which the Sabres announced captain Jack Eichel will miss the remainder of the season with a herniated disk. Eichel has been out since March 7.