Swedish midfielder Kristoffer Olsson in rehab after brain illness

The midfielder fell unconscious in his home on February 20th and was admitted to Aarhus University Hospital, where he was placed on a ventilator.

Tests showed he had suffered several small blood clots in the brain due to "an extremely rare inflammation" of the blood vessels in the brain, according to his club FC Midtjylland.

"Kristoffer has not yet regained either motor functions or his verbal abilities. The specialists estimate that the rehabilitation period will extend over several months," the club said in a statement.

"Kristoffer has now been phased off of ventilators and has therefore been transferred to Hammel Neurocentre ... specialised in advanced rehabilitation of neurological disorders."

The statement said it was "still too early to give a definitive prognosis."

Hailing from Norrkoping on Sweden's east coast, Olsson made his competitive debut for Arsenal in 2013, and has since played for Danish side Midtjylland and AIK in Sweden, then Krasnodar and Anderlecht, before rejoining Midtjylland permanently last summer after a loan spell.