Andrew Trimble faces month on sidelines after hand surgery

Ulster winger Andrew Trimble will be out of action for four to five weeks after undergoing hand surgery.

Trimble had already been ruled out of Ireland's final two Six Nations matches against Wales and England because of the injury sustained against Treviso.

Darren Cave, Louis Ludik and Stuart McCloskey are also unavailable for Ulster's rearranged Pro12 game against Zebre at Kingspan Stadium on Saturday.

Alan O'Connor should play at lock, with Rodney Ah You a likely replacement.

Both second row O'Connor and prop Ah You are set to return after injuries, while back Jacob Stockdale may reclaim a starting berth after being named on the bench for last week's win over Treviso in Belfast.

Jared Payne has been struggling with an ankle injury suffered against the Italians but has not yet been entirely ruled out of playing a part in Ireland's Six Nations encounter with Wales in Cardiff on Friday, or alternatively playing for Ulster a day later.

Ulster go into the game in need of a bonus-point victory to boost their chances of securing a top-four spot which would ensure their participation in the end-of-season play-offs.

The Irish province currently lie fifth in the table after four consecutive wins in the competition but a win on Saturday in their match in hand would see Les Kiss's side leapfrog the Scarlets into fourth position.

The match was originally due to be played on 25 November but was postponed because of a frozen pitch at Kingspan Stadium.

After tackling Zebre, Ulster have a week off, before facing a difficult run-in with fixtures against Dragons, Cardiff Blues, Munster, Ospreys and Leinster.

For their part, bottom-placed Zebre hope to overhaul Treviso in the battle to secure a Champions Cup place for next season, with two points currently separating the sides.

Ulster defeated Zebre 40-17 when the sides met in Italy on 26 February.