Cillian Willis is a cousin of Ireland skipper Brian O'Driscoll

Ulster have continued their rebuilding for next season by signing South African star Robbie Diack and Leinster scrum-half Cillian Willis.

Diack, who has joined on a three-year contract, is a 22-year-old former Stormers number eight.

Willis is a year older, has played at underage level for Ireland and arrives at Ravenhill on a one-year deal.

Queensland Reds pair Clinton Schifcofske and Ed O'Donoghue signed for the province earlier this week.

Ulster coach Matt Williams is in the process of filling the massive void left following the departures of Justin Harrison, Tommy Bowe, David Humpreys, Neil Best, Roger Wilson, Mark Bartholomeusz and Kieran Campbell.

"I'm extremely excited about the move to Ulster," said Diack.

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"My experience playing for the Stormers and Western province over the past three years has been fantastic and I feel 100% positive that my move to Ulster will be just as good and it will help mould me into a better rugby player."

"What I'm looking forward to most is the different style of rugby played in Ireland."

Playing in front of the famous Ravenhill crowd is a major attraction for the Dublin-born Willis.

"It is an exciting time for the province with a young squad and new coach and I'm looking forward to being part of it next season.

"Ulster has some of the most loyal supporters and they have made Ravenhill a very intimidating place to play, it will be good to experience that atmosphere at the ground and this time be on the right side of it.

"I've met with Matt Williams a few times recently and I'm thrilled about working under such a well respected coach, the lads that I have played alongside at Leinster all speak very highly of him."