(Reuters) - The National Basketball Association (NBA) postponed three more games and the National Hockey League (NHL) once again pushed back the Dallas Stars’ season opener, amid a surge of COVID-19 cases that has put professional sport on notice in North America. Two games between the Cleveland Cavaliers and Washington Wizards set for Sunday and Monday were on hold, the NBA said on Friday, because the Wizards did not have the “league-required eight available players to proceed” due to ongoing contact tracing on the team. Hours later, the NBA halted a Friday game between the Memphis Grizzlies and Minnesota Timberwolves, citing a similar shortfall of available players on the Minnesota team, making it the 12th game since Sunday that the league has postponed. Sixteen new players have tested positive for COVID-19 since Jan. 6, the NBA said on Wednesday, after the league and its players’ association agreed on Tuesday to “additional measures” to protect players and staff. Both the NBA and the NHL are adapting to the harsh reality of life beyond the quarantined “bubble” settings they used to close out their respective seasons last year, roughly 10 months since the coronavirus pandemic put most sport on hold. The NHL on Friday delayed the Dallas Stars’ 2020-21 season opener after a team-wide outbreak in which 17 players tested positive, and the team is now expected to open against the Nashville Predators on Jan. 22. The United States is experiencing a surge of novel coronavirus cases, and vaccine shortages and delays are further confounding the fight against the pandemic. The National Football League (NFL), which saw numerous delays but no outright cancellations during its regular season, reportedly plans to assign COVID-19 monitors here to the final four teams ahead its AFC and NFC title games, as it pushes toward a Feb. 7 Super Bowl game with little to no wiggle room for delay.