Tommy Bowe has been ruled out of Ulster's Guinness Pro 12 derby against league leaders Leinster this weekend.

The province have confirmed the Irish international has suffered a mild knee reaction following the game against Zebre when he made his first competitive of the season for them.

An injury plagued campaign saw Bowe miss out on the entirety of Ireland's Six Nations campaign following posterior cruciate ligament and meniscal injuries to his right knee during the 2015 World Cup quarter-final loss to Argentina.

Meanwhile, Nick Williams has played his last game for Ulster after accepting defeat in his attempt to rehab a shoulder injury.

The powerful flanker will now have to undergo surgery to correct the problem ahead of his move to the Cardiff Blues this summer.