BOSTON (CBS) — With all the uncertainty surrounding Kyrie Irving’s sore left knee, the Celtics will reportedly request another injury exception from the NBA.

Irving is set to have a “minimally invasive procedure” on his knee on Saturday, and the Celtics are hoping to have a better idea of how much time their All-Star guard will miss after the operation. But chances are he’s going to miss some time, and the Celtics could use another player to fill out their depth chart for the final few weeks of the season.

So they’ll be reaching out to the league for a replacement player exception, according to the Boston Herald’s Mark Murphy.

To get that exception, a team must have four players expected to miss two weeks due to an injury. Irving has already missed two weeks, so it would appear the Celtics don’t anticipate having him back anytime soon. The Celtics have three other players who fit that criteria: Gordon Hayward, Daniel Theis and Marcus Smart. All three will miss the rest of the regular season, with Smart hopeful that he can return from a UCL tear in his right thumb for the playoffs.

The Celtics were granted a disabled player exception by the NBA after they lost Hayward on opening night, which they used to sign center Greg Monroe. But the replacement player exception is a bit different.

If the exception is granted by the NBA, Boston will be able to add an additional player to their roster for the regular season. That player will not be eligible to play in the playoffs, and would have to be waived if Irving returns before the end of the regular season.