Queens Park Rangers midfielder Samba Diakite has returned home to France to battle depression.
It is unclear what has triggered the problem, but Rangers will give the 23-year-old as much time he needs to recover.
The Mali man started QPR's first two Premier League matches but missed last weekend's clash against Manchester City without any explanation.
It is thought Diakite was given 10 days leave after the 1-1 draw at Norwich on August 25. However, 13 days after going to France, he is yet to return.
It is unclear whether Diakite will be available for the clash against Chelsea a week on Saturday.
QPR's club doctor has made regular trips across the channel to check on the midfielder, who is on a specially devised fitness regime in France.
Hughes made Diakite one of his first signings as manager in January - and he played a key role in the club's top-flight survival last season while on loan. QPR paid £3.5million for Diakite in the summer.
His case further highlights the problem of depression among footballers. The Professional Footballers' Association sent a booklet on how to handle the illness to their members last season.