Leo Cullen claims Roman Salanoa told him he was staying in Dublin only for the prop to sign for Munster and leave Leinster short on tighthead cover.
It has been a frustrating near 14-month stint on the sidelines at Munster for their injury-plagued out-half Joey Carbery.
The movement of players from Leinster to the other provinces has at times been a source of frustration for the club.
Ulster maintained their 100 per cent start in the Guinness PRO14 as they began the new year by beating Irish rivals Munster 15-10, although they were made to fight all the way at the Kingspan Stadium.