BOSTON — The first time Doc Rivers watched film on Myles Powell was Saturday.

The first time the 76ers coach met Powell was Monday evening inside TD Garden.

The first message Rivers delivered to Powell less than two hours before making his NBA debut was, “Hey, we’re playing you tonight.”

“He asked me, ‘What should I run?’” Rivers recalled. “I said, ‘The floor.’”

Powell immediately getting thrust into his first NBA action the night after signing a two-way contract with the Sixers exemplifies another strange 36 hours for a team again depleted by injuries and players isolating in health and safety protocols.

» READ MORE: Sixers outlast Boston Celtics in matchup of teams decimated by COVID-19 and injuries

Sunday’s scheduled home game against New Orleans was postponed less than six hours before tip-off, one of five NBA games pushed back as COVID cases surged across the league and country. Though the Sixers had enough players to face a Boston team that was also shorthanded on Monday, their second unit of Powell, Isaiah Joe, Charles Bassey, and Aaron Henry was barely recognizable. Yet they survived this particular night, with Joel Embiid’s 41-point performance lifting the Sixers to a 108-103 win.

“Everything’s day by day right now,” Rivers said. “And not just us. Boston’s going through it. A lot of teams are going through it. It’s all uncharted. Each year, so far with this COVID, feels like it’s different, and this is another one. So we just learn as we go. It’s tough, though, because you’re trying to win games.”

It’s the latest twist during the NBA’s third consecutive pandemic season. As of Monday night, more than 100 players had entered health and safety protocols this season, with more than 85% of those occurring in December. The staggering figures reflect the sharp uptick in cases with the arrival of the omicron variant, as well as a workplace that tests far more regularly than the general public.

Rivers was not optimistic that Sunday’s scheduled game against the Pelicans would be played at that morning’s shootaround, when player-development coaches were running sets with seven Sixers. Backup point guard Shake Milton and backup center Andre Drummond had joined reserve forward Georges Niang in protocols, while reserve guard Furkan Korkmaz remained out with a non-COVID illness, and Embiid (ankle), starting point guard Tyrese Maxey (quadriceps) and starting wing Danny Green (hip) were all listed as questionable to play.

“I was like, ‘What the heck is this?’” standout forward Tobias Harris said. “ … We were looking around like, ‘Man, I know a couple people in Philly that could just come in this gym and help us give us a body right now.’”

By 1:30 p.m. Sunday, the game against New Orleans had been postponed. Rivers watched the NFL on television. Embiid spent time at home with his family. Harris went on a quest to find Nintendo Switch portable gaming systems for families he is sponsoring for Christmas.

Meanwhile, Powell, Henry, and Paul Reed were added to a group chat from the G League Showcase in Las Vegas. They played in the Delaware Blue Coats’ 126-101 victory over the Fort Wayne Mad Ants that afternoon, then flew out to Boston in time for Monday’s Sixers game. They were about to turn the “next man up” cliche into practice.

“It all happened so fast,” Henry said. “But it’s what the NBA’s about, being able to adapt on the fly and be able to adjust.”

Added Rivers: “I feel no sympathy. … If they called me from Timbuktu and I knew I had a chance to play, there would be no complaining in that. I would be eager to play, and I assume that’s how they are.”

Back in Philly, the Sixers could not get their charter flight originally scheduled to depart following Sunday’s game moved up, putting them in Boston late Sunday night. They did not hold a morning shootaround on Monday. Uncertainty swirled throughout the day about the status of the Celtics’ roster, given their lengthy injury report. Rivers also fielded a couple of calls from retired players who hoped to cash in on the NBA’s new rule allowing teams to sign players to 10-day contracts to replace those in protocols, telling at least one, “You gotta be freaking kidding me. … You can’t play basketball. Are you talking about a round of golf?”

By 5:20 p.m. Monday, the TD Garden court was populated by Henry and Powell working on strength exercises along the baseline. Bassey and Reed sat in courtside seats and watched film with coaches holding laptops. Joe and Matisse Thybulle moved along the three-point arc to launch shots. Then Thybulle, Henry, and Powell joined Bassey and Reed in those chairs, dissecting tendencies of opposing players expected to see minutes such as Payton Pritchard and Romeo Langford, as well as just-signed C.J. Miles and Justin Jackson.

With no Maxey or Milton, Curry became the Sixers’ de facto point guard and finished with 26 points on 10-of-14 shooting and seven assists. Harris rebounded from a poor shooting performance Thursday in Brooklyn and totaled 25 points and seven rebounds. Joe was the game’s first sub, replacing Green. The second quarter began with a lineup of Powell, Joe, Henry, Harris, and Bassey, a group that had never practiced together. Though the Sixers only scored one bench point in the game, Rivers was pleased with the unit’s defensive intensity and ability to play without mistakes.

Embiid took over in the fourth quarter, when he scored 17 points. He hit a challenging fadeaway in the corner, intercepted a pass and sank three free throws in the final seconds to seal the victory.

Rivers hopes that someday his team gets a “rash of health,” the opposite of the rash of injuries that can thwart a season. Until then, the coach is calling this stretch a “battle of the fittest.”

At the conclusion of these bizarre 36 hours, the Sixers prevailed.

“I’m just trying to get through these games and see if we can win some of them,” Rivers said. “… It is what it is. There’s nothing you can do about it.”