Nabokov left the Islanders' 4-3 win over Montreal on Thursday 7:55 into the first period after suffering the injury. The 36-year-old made a save with his right pad on Montreal's Yannick Weber and went down immediately afterward in obvious pain.
Backup Rick DiPietro came in to replace Nabokov, making 24 saves in relief to record his second win of the season.
DiPietro made his first appearance of 2011-12 to replace an injured Nabokov as well. The 30-year-old goalie, who was sidelined with a concussion to begin the season, was thrust into the game during the shootout in the team's 3-2 loss to the Penguins Oct. 27.
Nabokov left that game with a groin injury as well -- he missed almost two weeks as a result -- though it is not immediately clear if the two injuries are related.
Nabokov's injury should provide clarity to the Islanders' murky goaltending situation. Coach Jack Capuano has elected against naming a clear-cut starter among the three on their active roster -- Al Montoya is also competing for playing time -- but may tip his hand now that only two are available.
DiPietro, who has recorded two straight wins, is 2-1-2 with a .900 save percentage and a 2.85 goals-against average. Montoya, who was awarded the opening-night nod and the following two starts, is 2-2-1 with a .926 save percentage and a 2.44 GAA.
Since being claimed off waivers last January and subsequently suspended by the Islanders for refusing to report, Nabokov has been speculated as trade bait for general manager Garth Snow.
But rumors that circulated last week -- Nabokov to Columbus in exchange for defenseman Fedor Tyutin -- were vehemently denied by Snow to ESPNNewYork.com.
Katie Strang covers the NHL for ESPNNewYork.com.