Dallas Mavericks rookie Dereck Lively II has been placed in a walking boot after suffering a sprained left ankle on Saturday in a win over the Portland Trail Blazers.

Lively suffered the injury midway through the first quarter. He appeared to step on a defender’s foot after attempting to haul in a rebound on offense near the rim. He was eventually ruled out of returning to the game after six minutes of playing time.

He recorded two rebounds before suffering the injury.

“There is no timeline (for his return),” Mavericks coach Jason Kidd said prior to facing the Denver Nuggets on Monday. “It is good to see him without the crutches, just in a boot. I think we’ll know more as we get home, but he is in good spirits.”

Lively has emerged as a key player for the Mavericks. He has started in 22 of his 23 games played this season, averaging 8.9 points, 7.7 rebounds, 1.6 blocks and 1.1 assists on 73.4% shooting from the field. He leads the league in field-goal percentage and is third in blocks among rookies.

The Mavericks wrap up their two-game road trip in Denver. They host the Los Angeles Clippers on Wednesday and should have the opportunity to evaluate Lively further once they return to Dallas.

Story originally appeared on Rookie Wire