Ulster are understood to have explored the possibility of bringing Springbok out-half Elton Jantjies to Belfast only to be met with a lukewarm response from the IRFU.
All Black Charles Piutau is set to join Bristol this summer, freeing up a place for a new import at Kingspan Stadium, and the northern province have been on the lookout for reinforcements in the No.10 jersey since Paddy Jackson had his contract revoked by the IRFU after being acquitted of rape in March.
They began last season by bringing in Australian Christian Leali'ifano on a short-term deal but, after a similar move for former All Black Stephen Donald fell through, finished the campaign with only Johnny McPhillips as a specialised 10.
But it is believed that the possibility of signing Jantjies has been met with reluctance.
The IRFU must sign off on all players and favour Ulster recruiting an Irish-qualified signing to aid the national side's preparations for next year's World Cup.
Leinster's Joey Carbery is back-up to Johnny Sexton at Test level but has played little rugby at 10, instead being selected at full-back.
The 22-year-old has seemed reluctant to move north despite the promise of more game time and, if he does leave, Munster now seems a more likely destination next season.
Jantjies has been South Africa's starting out-half for much of the two years since Ireland visited in 2016, although he did lose his place to Handre Pollard last November.
A playmaker rather than a game-manager, the 27-year-old represents the Lions in his homeland, but his present deal runs only until the end of the Super Rugby season in August.