Williams suffered a knee injury during his sixth game against the Trail Blazers on Sunday.

Robert Williams will undergo surgery on his right knee during the season. Amanda Loman/Getty Images

Robert Williams’ first season in Portland ends just a few weeks into the regular season.

The former Celtics center will undergo season-ending knee surgery to repair his kneecap and ligaments. ESPN’s Adrian Wojnarowski reported this on Friday.

Williams, now with the Trail Blazers, faced the possibility of season-ending surgery after suffering a right knee injury during the team’s loss to the Grizzlies on Sunday. In the fourth quarter of that game, he hit his right knee in a collision with Grizzlies big Jaren Jackson Jr., causing his kneecap to move out of place and damaging a ligament, according to The Athletic. The Trail Blazers cleared his knee on Monday and later that day it was reported that Williams would undergo either surgery to clear the knee that would allow him to return after a few months or surgery that would end his season.

This is the second notable knee injury Williams has suffered in recent seasons, but both involved different knees. He tore the meniscus in his left knee in late March 2022, missed about a month of action, and played much of their playoff run to the NBA Finals that year with the Celtics. He had to undergo a second surgery on that knee in September 2022 for a cleanup, which kept him off the floor until December of last season.

The Celtics traded away Williams as part of the deal to land Jrue Holiday, which also included moving Malcolm Brogdon and two first-round picks in the October trade.

Williams, who turned 26 later in October, became a fan favorite in Boston not long after the Celtics drafted him in 2018 and earned the nickname “Time Lord” from the fanbase during his rookie season. His game also grew on fans because of his ability to make highlight plays above the rim with flashy dunks and blocks. He also proved valuable during the 2021-2022 season, leading the league in defensive rating that season.

Williams played off the bench in all six games he played for the Trail Blazers this season, scoring 6.8 points and grabbing 6.3 rebounds per game. He also added 1.2 blocks and 1.2 steals in 19.8 minutes per game, with Portland going 2-4 in the games he played.

Although Williams had just arrived in Portland, several other teams were eyeing him as a possible trade candidate before the February deadline, Wojnarowski said.