Although it appeared Nielsen was ready to come off injured reserve and play Thursday, he left the ice early during the morning skate after feeling a pinch and has not practiced since.
The Islanders never activated him off injured reserve as originally planned.
Nielsen has five goals and 14 assists in 37 games for the Islanders this season.
Sim pact terminated
Jon Sim, who was placed on unconditional waivers Thursday, cleared at noon Saturday and his contract was terminated, the Islanders confirmed.
Former Blackhawks goaltender Cristobal Huet also plays for Fribourg-Gotteron.
Sim, 33, was suspended Thursday and essentially released after refusing to report to the Islanders' AHL affiliate in Bridgeport on Tuesday for what would have been his fourth minor-league stint this season. The scrappy journeyman had one goal and three assists in 34 games for the Islanders.
Sim told Newsday on Friday that he will make a decision after this season in Switzerland about whether to try to return to the NHL.
Depth defenseman Dylan Reese was placed on waivers Friday and cleared them Saturday. The 26-year-old Harvard grad was not sent to Bridgeport and remained with the team as a healthy scratch Saturday night pending any other moves . . . Kevin Poulin was the backup goaltender Saturday night with Nathan Lawson scratched.