Marcell Coetzee is set to be released from his Ulster contract at the end of April.
The South African back row star is due to join the Bulls in July but a thigh injury sustained earlier this year has brought an early end to his stay at the province.
Coetzee had originally hoped to return for the end of the Rainbow Cup to make a swansong in an Ulster jersey - which could have acted as his bid for selection to the Springboks squad due to take on the Lions this summer - but it is now evident that he has played his final game for the side.
That was the PRO14 game against Leinster at the start of March, in which he was forced off after 33 minutes with the hamstring injury that has curtailed the final months of his Ulster stay.
Over his five years at Ulster, Coetzee has played 57 times and scored 15 tries.
Head of Rugby Operations and Recruitment, Bryn Cunningham, said: “We have come to an agreement that will allow Marcell the time and space required to continue his rehab.
“I’d like to thank Marcell for his contribution to the province over the past five years and we wish him and wife, Chanelle the very best for their upcoming return home to South Africa.”
News of Coetzee's move to the Bulls emerged on Christmas Day and was confirmed by Ulster the following day.
At the time, Coetzee explained: “It all started during lockdown when I was back home for four months. My wife and I did a lot of thinking together about life and we also reflected on where I am in my career.
“We decided to come back to Belfast with an open mind, but ultimately we miss home, the South African culture and way of life – and after five seasons the longing for home has just caught up with us.
“I must say Ulster have been absolutely superb to me, on and off the field during my career, and I feel I have grown as a person and as a player for the experiences the club has given me. Ulster will always have a special place in the hearts of my wife and I.”
Coetzee has become widely recognised as Ulster's top player and would have been a part of South Africa's 2019 World Cup win had it not been for an untimely ankle injury sustained in a warm-up game.