Tommy Bowe has conceded defeat in his bid to be fit in time for the 2016 Six Nations for Ireland.
Bowe suffered a knee ligament injury during the 2015 Rugby World Cup quarter-final against Argentina and the 31-year-old is working his way back to full fitness.
Despite missing the Six Nations, Bowe still hopes to make an impact later in the season for Ulster.
"Unfortunately it's a slow process and to rule yourself out of the Six Nations is disappointing," Bowe told the BBC.
"I have to concentrate on getting myself back to where I was and there's no point in rushing it.
"To be back by the start of February is unlikely but I'm still pretty positive I can add something to Ulster's season."