Already missing Joni Pitkanen, who also sat out Wednesday night's home loss to Nashville with a sore left hip flexor, the Flyers were without Mike Rathje. The 32-year-old defenceman has been limited to 18 of Philadelphia's first 26 games this season.
While Pitkanen is considered day-to-day, Rathje's injury appears more serious. Flyers trainer Jim McCrossin said on Thursday that Rathje is out indefinitely because of Piriformis Syndrome - a condition that causes backside pain.
Rathje, who has just one point this season, had none in three games since he missed the Nov. 22 contest against Ottawa with the same ailment. He heard boos every time he touched the puck Wednesday night after his late, third-period turnover led to the deciding goal in Nashville's 3-2 victory.
Rathje, in the second season of a five-year, US$17.5 million deal that includes a no-trade clause, missed five games in October with what was deemed a back injury, and another in November with Piriformis Syndrome.
He has no goals and a minus-7 rating this season.
Jonsson posted two assists in four games earlier this season with the Flyers. While with the AHL's Philadelphia Phantoms, the 24-year-old defenceman had six assists in nine contests. He missed the first eight games there due to a high right ankle sprain.
The Flyers were also without forward Geoff Sanderson, who sat out against the Islanders with a groin injury sustained Wednesday against Nashville. Sanderson, Philadelphia's second-leading scorer with 17 points, played in all but one of the Flyers' first 25 games.