"He's got a broken bone that's going to take some time to heal," coach Dave Tippett said, adding that surgery is not required. "He's disappointed; tough break for him."
Larsson is entering his ninth NHL season, including his fourth with Edmonton. He appeared in 82 games last season, with three goals, 17 assists and 44 penalty minutes. When the Oilers traded Taylor Hall for Larsson in 2016, he was seen as a building block of a Stanley Cup team. But Edmonton has made the playoffs just once in his tenure.
The Oilers opened the season with a 3-2 win against Vancouver on Wednesday.
To take Larsson's spot, the Oilers recalled defenseman Evan Bouchard -- a highly touted 2018 first-round draft pick. In a corresponding move, the Oilers assigned defenseman Ethan Bear to Bakersfield of the AHL.