U.S. Markets closed

Sources: Celtics' Daniel Theis has torn left meniscus, will undergo season-ending surgery

Rookie Daniel Theis has been a solid contributor for the Celtics. (AP)

Boston Celtics rookie center Daniel Theis has suffered a torn meniscus in his left knee and will undergo season-ending surgery, league sources told Yahoo Sports.

Theis underwent further testing Monday morning after suffering the injury in Sunday’s home loss to Indiana. The 6-foot-10 center emerged as a critical part of the Celtics’ rotation this season, averaging 5.3 points and 4.4 rebounds in 63 games. He has helped bolster Boston’s frontcourt unit as a floor-spacer and defensive presence, along with Aron Baynes and Greg Monroe behind starter Al Horford.

Play Tourney Pick’em | Fill out your bracket | Print it | Play against Draymond Green

Boston (46-21) currently has a firm grip on the second seed in the Eastern Conference, but lost Theis, Marcus Smart and All-Star guard Kyrie Irving to injuries in Sunday’s loss to Indiana.

Theis, 25, joined the Celtics last offseason after playing internationally in Germany. He has also had an extensive career with the German national team.

More from Yahoo Sports:

Did a Lakers usher really not recognize Jack Nicholson?
How the NCAA’s mistake could lead to historic tourney upset
Heartbreaking photo shows sad side of March Madness
Short deal for QB Cousins could go long way for elite NFL platyers