Sean O'Brien is set to leave Leinster for London Irish after this year's World Cup.
RTÉ Sport understands the move to London Irish will be confirmed next week, with the 'Tullow Tank' set to link up with former Ireland head coach Declan Kidney and Les Kiss at the Reading-based club - who are nine points clear at the top of the Championship.
The back-row forward will turn 32 next month and was unlikely to see his IRFU central contract renewed on a multi-year basis.
According to Rugbypass.com, O'Brien has been offered a three-year contract worth £450,000 (€514,000) per annum by London Irish, who look set to make a return to the Premiership next season.
Captain Rory Best, speaking at Murrayfield head the Six Nations clash with Scotland tomorrow, was asked about the possibility of O'Brien moving on.
He said: "We obviously haven't heard anything, that's Seanie's own contract negotiations are his own business and I think it would be wrong of me to comment on somebody's personal situation.
"All you can say from a player's point of view is that you know and you trust the players weigh up the situation and ultimately do what is right for them and their families."
Despite some bad luck with injuries, the Carlow native has played 58 Tests - including five for the British and Irish Lions. His star quality and nationality will be a big selling point at the Madejski Stadium, where he will be joined by Australians Nick Phipps and Curtis Rona next season.
The move is unlikely to affect O'Brien's World Cup prospects, as he is centrally contracted to the IRFU until the conclusion of the tournament.
Selected to start tomorrow against the Scots, O'Brien's situation is similar to Paul O'Connell ahead of the 2015 World Cup - when the then Irish captain had agreed to join Toulon ahead of the tournament.
However, while there is no official policy regarding the selection of players based outside Ireland, it is unlikely O'Brien will be considered for the 2020 Six Nations by Andy Farrell, who will replace Joe Schmidt as Ireland head coach after the World Cup.
Ian Keatley and former Ireland Under-20 duo Conor Gilsenan and Brendan Macken are currently on the books of London Irish. Former Munster fly-half Keatley will play Pro14 rugby for Benetton for the 2019-20 season.
Keatley has yet to play for the Exiles but could may his debut this weekend as he is named amongst the replacements for Saturday's game with Bedford Blues.