The outsider governed starting center Dereck Lively II Just four minutes into Tuesday’s game against Denver, he was sidelined with a sprained ankle, the team announced (via Twitter).

Lively continues to build on an impressive first season in which he finished sixth in Rookie of the Year voting and helped the Mavericks reach the NBA Finals. In 31 games (24 starts) this season, he averaged 9.3 points, 8.1 rebounds, 2.7 assists and 1.7 blocks while shooting a highly efficient 70.1% from the field.

It’s a tough blow for a Dallas team that already lacks a superstar Luka Doncicwho is dealing with a calf injury that is expected to keep him out until this month at the earliest. According to Grant Afseth of Dallas Hoops Journal, Doncic is on track to return in early February.

Lively’s most direct replacement is obvious: Daniel Gafford. He and Lively often alternate at the starting center position, with Gafford starting in all 22 of his appearances last postseason and Lively taking over this year. Beyond Gafford, the Mavs did it Maxi glue, PJ Washington And Dwight Powell as a big one. Powell came into the game in the first half on Tuesday after not playing in the previous two games for Dallas.

It’s unclear exactly how much time Lively will miss, but sprains are typically measured in weeks rather than days as recovery time, although that’s not always the case. The Hornets’ Tidjane Salaun suffered a sprained ankle in December that only sidelined him for two games, a little over a week. The Warriors are now ahead Jonathan Kuminga suffered a more serious illness that will sideline him for at least three weeks.