Niskanen informed the Flyers that he will retire ahead of the 2020-21 campaign, Elliotte Friedman of Sportsnet reports.

Niskanen scored a goal on his lone shot in Tuesday's 4-3 overtime win over the Islanders in Game 5. He also had one hit and one block with a plus-2 rating.

Niskanen served his one-game suspension in Friday's Game 6 win over the Canadiens.

Niskanen was suspended for Friday's Game 6 matchup against the Canadiens for Cross-checking forward Brendan Gallagher per The NHL's Department of Player Safety

Niskanen will have a hearing with the league for his cross-check on Hab's Brendan Gallagher, per the NHL Department of Player Safety.

Niskanen had eight goals and 33 points with a plus-15 rating in 68 games prior to the coronavirus halting play in March.

Niskanen recorded an assist, three shots on net, three blocks and a plus-3 rating in a 4-2 victory over the Sharks on Tuesday.

Niskanen scored an empty-net goal and fired four shots on net in Monday's 3-0 win over the Red Wings.

Niskanen picked up two assists, one on the power play, in Friday's 4-3 overtime loss to the Penguins.

Niskanen posted an assist, three shots on goal and five hits in Thursday's 5-4 loss to the Golden Knights.