The 24-year-old McAvoy is the team's top defenseman. He has two assists in three games and is Boston's leader in playoff ice time with a 25:15 average. The Bruins deployed him against the Hurricanes' top line centered by Sebastian Aho in Game 3, a 4-2 win for Boston in which that line was held scoreless.
Even without McAvoy, the Bruins were able to even the series 2-2 with a 5-2 victory Sunday.
McAvoy was replaced in the Boston lineup with Josh Brown, 28, whom the Bruins acquired from the Ottawa Senators at the trade deadline. His last postseason appearance was with the Florida Panthers in 2020. Brown was on the ice for 12:52.
After the All-Star Break, the NHL and NHLPA agreed they would stop testing asymptomatic players and that testing will continue only on a limited "for cause" basis in fully vaccinated players, which suggests McAvoy had to be symptomatic to be tested.
Under NHL COVID-19 protocols, players will be allowed to leave isolation after five days if they produce a negative test and are asymptomatic. Game 5 is scheduled for Tuesday night in Raleigh and a possible Game 6 is scheduled for Thursday in Boston.
Bruins coach Bruce Cassidy said that injured defenseman Hampus Lindholm could return for Game 5 back in Raleigh.
The Hurricanes, meanwhile, received good news with word that Antti Raanta was back in goal. He left during Game 2 after a collision with Bruins forward David Pastrnak. Raanta stopped 23 of 27 shots in Sunday's Game 4 loss.
Rookie Pyotr Kochetkov took over in goal and got the win in Game 2, but lost Game 3.
Kochetkov is actually the Hurricanes' third-string goalie; Raanta is the backup to Frederik Andersen, who has been rehabbing a lower-body injury.