Now one of five South Africans in the Ulster squad, Diack will find himself eligible to play for Ireland come July having been resident in the country for the requisite three-year period.
The talented forward has had a big start to the season, winning a man-of-the-match award for his display in Ulster's opening Heineken Cup match against Aironi earlier this month, and despite considerable competition for places in the back row, he has featured in all but one of Ulster's competitive matches so far.
Strong-tackling centre Cave has also had significant game-time for Ulster so far this season. He won his 50th provincial cap against Edinburgh last month, but missed last weekend's trip to Biarritz Olympique with a hamstring injury.
A product of Ulster's Academy system, Cave signed his first contract with Ulster in 2008 and won his first Ireland cap against Canada during the 2009 summer tour to North America.
BJ Botha's involvement in South Africa's Tri Nations campaign gave Fitzpatrick a real opportunity at the start of this season and the powerful tighthead prop, who hails originally from Moseley in the West Midlands, grabbed it.
While a calf injury, sustained against Aironi in the Magners League, has ruled Fitzpatrick out of contention since, his performances for Ulster in the pre-season and early season games were making many sit up and take notice.