Dallas Mavericks star Kyrie Irving has a bulging disk in his back and is expected to miss at least one to two weeks, sources told ESPN.

There is optimism that treatment over the coming days will provide a return-to-play target date, sources said.

The Mavs announced Sunday that Irving would miss Monday’s game against the Memphis Grizzlies with a lumbar sprain in his back. He did not join the team on the road trip, remaining in Dallas to be reevaluated, sources said.

Irving did not play in Friday’s home loss to the Cleveland Cavaliers, when he was ruled out hours before tipoff with an illness.

Dallas is already down one superstar, as guard Luka Doncic has been out since suffering a strained left calf during the Christmas Day loss to the Minnesota Timberwolves. Doncic, who was seen using a scooter to move around at the arena Friday night, is expected to be reevaluated in the final week of January.

The Mavs, who also dealt with suspensions to forwards Naji Marshall and P.J. Washington stemming from a Dec. 27 altercation with Phoenix Suns center Jusuf Nurkic, have lost four consecutive games entering Monday night. Dallas (20-15), the defending Western Conference champion, is 0-3 when missing both Doncic and Irving this season.

Irving, 32, has performed at an All-Star level in his 14th NBA season, averaging 24.3 points, 4.6 rebounds and 4.9 assists per game while shooting 49.0% from the floor and a career-best 44.1% from 3-point range.