Back pains forced Calle Halfvarsson to withdraw from the World Championship's last race in Lillehammer, 20 km skiathlon.
The skiing star now knows what is behind the injury that he has been struggling with at the beginning of the season.
"It's a disc that's affected, and which in turn irritates the nerve root," says national team doctor Rickard Noberius in a statement from the Swedish Ski Association.
"The prognosis looks promising, and with rehabilitation, Calle can be ready for competition in the near future."
The 35-year-old says that "the news is sad" but that it "is still going in the right direction."
Halfvarsson will miss this weekend's competitions in Davos, Switzerland, but is aiming for the Tour de Ski, which starts on December 28.
"But the priority is first and foremost to get well for the World Championship in Trondheim, which is the winter's big goal," he says in a statement.
