Zlatan Ibrahimovic's heel injury has been described as "inexplicable" by Sweden's team doctor as the Paris Saint-Germain striker continues his battle to return to fitness.
Ibrahimovic, 33, has said that a decision on whether he will participate in his country's Euro 2016 qualifier with Russia in Stockholm on Thursday will be made at the last minute to give him the maximum possible time to recover from a problem that has sidelined him since Sept. 21.
The forward, who has struck five Ligue 1 goals in as many games for PSG this season, has missed his club's last four competitive outings with the heel injury.
But Sweden team doctor Leif Sward told reporters that he and his staff could not find the reason for Ibrahimovic's struggles, despite the player undergoing an MRI scan.
"We have carried out medical examinations, and the injury is inexplicable," he said.
"There are no major signs of inflammation, but he feels pain. We don't want the injury to get worse, an Achilles tendon can snap.
"Zlatan is getting better and better, but he won't play with a painkilling injection."