New Oxford United signing Patrick Hoban could be sidelined until February after damaging ankle ligaments in training.
The 23-year-old striker joined the club on a free transfer from Irish side Dundalk last month but was not eligible to play for Oxford until 1 January.
Head coach Michael Appleton told the club website: "We all feel for Patrick.
"He has settled in really well. He just went up for a header and came down on his ankle. There was nobody near him, it was just one of those things."
Hoban, who was released by Bristol City in 2011 without making a senior appearance for the Robins, turned down a trial at Scottish Premiership side Kilmarnock before joining Oxford.
Appleton added: "He's a strong lad and will come back fit and raring to go but for now we just have to wait and see how that injury settles down."