Ten NBA referees, including veteran officials typically assigned to the NBA Finals, are sidelined because of issues related to COVID-19 and, in one case, an injury, a league official told ESPN.

That figure represents the highest of its kind to date in a season during which 24 referees have missed at least one game because of health and safety protocols, a league spokesman told ESPN.

Most of the absences have been tied to contact tracing, according to the spokesperson, who added that the league expects all 10 of the referees currently sidelined to be available for the playoffs, which start in less than a month.

"We at the NBA have taken a very strong stance, especially with referees traveling commercial, that we want referees and the teams that they are serving to be safe," Monty McCutchen, the NBA's vice president of referee development and training, told ESPN. "And so with an abundance of caution, we pull people out on contact tracing, if there's even the smallest inkling [of an issue]."

While teams travel via charter flight, referees fly commercially, exposing them to more individuals who could be carrying COVID-19. The referee absences have forced the league into more instances of two-person referee crews (rather than the typical three-person crews) than in seasons past, McCutchen said.

These absences also have led to six lower-level referees from the G League to work more NBA games this season than anticipated, according to McCutchen. Their officiating has become a hot-button issue for some team executives who say the quality of their officiating has negatively affected games.

NBA general managers have voiced their complaints -- what they feel are the wide variances of officiating -- to McCutchen throughout the season, league sources tell ESPN.

"It's been bad all year," one GM told ESPN.

Said a second GM about the replacement officials: "Young and inexperienced."

When asked whether the lower-tier officials have affected the quality of officiating, a third NBA GM said: "That's an understatement."

McCutchen, however, disputes that characterization.

"Our metrics and our data show that we're better this year, analytically, with our decision-making," McCutchen said. "These were our top six G League officials who would have been getting some NBA games anyway this year. They had to be pressed into some more service, but they are knocking on the door to being staff members.

"It's not like, 'Oh, let's just call any random G League [official] because they live in Portland and we'll pull them up that night.' They had already reached levels of excellence that meant they were ready for this."

In a typical season, lower-level officials -- those who are considered on the cusp of becoming NBA regulars -- might work six to eight games each, McCutchen said. But because of COVID-19-related absences, McCutchen said this season those officials have worked three times as many games, or roughly 20-25 games each.

"All six did a remarkable job," McCutchen said. "I'm very proud of their work."

McCutchen says roughly 20 NBA officials leaguewide of the 73 tasked with working games this season have less than five years of experience.

"There's been some need from [COVID] protocols to put crews together that maybe aren't on their normal cadence of growth," he said. "And I think that the league can understand that that's necessary this year."

Although some team executives have said they're concerned about how potential absences by veteran officials could affect the quality of officiating in the postseason, McCutchen said there will be safeguards in place.

One such safeguard is having additional alternate officials on standby, according to McCutchen, who also said the six G League officials will not work playoff games or games that are impactful to playoff races. The number of officials working postseason games will be trimmed, as usual, from 73 to 36 -- with the latter figure largely composed of the league's most experienced officials.

There's also hope that the spaced-out postseason schedule, along with an increasing number of referees who are vaccinated, will lead to fewer referees being sidelined in the playoffs.

McCutchen, who worked as an NBA referee for 24 years, said the league has offered health services and assistance for officials to be more easily vaccinated given their travel schedule. While he doesn't have figures on how many officials have had at least one dose of a vaccine, McCutchen said the "vaccination program is in full force right now."

"Now, clearly, COVID and the protocols -- the contact tracing, an inconclusive test that we have as an abundance of caution -- remove someone out of the rotation," he said. "We've been affected just like every other stakeholder has been affected: teams, coaches, players, GMs, referees. I think we're all dealing with very similar stresses."