Leinster skipper Isa Nacewa and fellow New Zealander Jamison Gibson-Park are set to miss the upcoming Pro 14 games against Southern Kings and Cheetahs after they were denied visas to enter South Africa.
New Zealand citizens were previously exempt from having to obtain visas when visiting South Africa, but these regulations were changed in mid-January.
Former Ireland Under 20 Nick McCarthy has been called up as a cover to the squad in Johannesburg as confirmed by a statement released by the club.
"Leinster Rugby can confirm that both Jamison Gibson-Park and Isa Nacewa have not been granted a visa at this point in time and will as a result return to Dublin at the earliest opportunity.
"Nick McCarthy has been called up to the touring squad as a result and will arrive tomorrow.
"Leinster Rugby will be making no further comment on this matter."
Leinster will face the Southern Kings on Saturday at Nelson Mandela Bay Stadium following which they will head to the Toyota Stadium to take on Toyota Cheetahs on 22nd September.
Leinster are currently at second in Conference B after they won both their games in the ongoing season of Pro 14.