The Boston Celtics saw their 13th player enter the NBA’s health and safety protocols in a little more than a week when guard Dennis Schroder entered Saturday, a couple of hours before the team is set to play the Bucks in a Christmas Day matinee in Milwaukee.

Schroder is one of nine Celtics — along with guards Josh Richardson and C.J. Miles, forwards Justin Jackson, Sam Hauser, Grant Williams and Aaron Nesmith and centers Enes Freedom and Bruno Fernando — who will be out for Saturday’s showdown because of health and safety protocols.

Another, center Al Horford, has exited the protocols but remains out as he ramps up his conditioning after missing more than a week.

Five other Celtics players who were questionable, however — guard Brodric Thomas and forwards Juancho Hernangomez and Jabari Parker due to protocols, and guards Marcus Smart and Romeo Langford due to injury — were declared available, giving the team 12 players for Saturday’s game.

Those 12 players include two — forward Al-Farouq Aminu and center Norvel Pelle — whom Boston signed earlier Saturday via hardship waivers to fill out the roster. The Celtics have now signed five players via hardship waivers over the past week to stay afloat amid their ever-rising COVID-19 case count.

Schroder, 28, is averaging 16.3 points and 4.7 assists per game in 29 games (including 18 starts) this season for Boston, which enters Saturday’s game with a 16-16 record.