Connacht lock Mike McCarthy has announced his intention to leave Connacht at the end of the current season to join Leinster.
McCarthy's current contract expires in June next year and Connacht CEO Tom Sears revealed his departure would be a loss to the Irish province.
"We are bitterly disappointed to lose Mike McCarthy, who has been a popular senior member of our squad," he said.
"While disappointed, particularly given the continued success of Connacht in recent years, we respect the individual player's decision and wish Mike every success in his future playing career."
Connacht have seen significant success in recent years both on and off the field.
With a growing fan-base and record match attendances, they have enjoyed notable victories in the last 12-months over Heineken Cup heavy hitters Biarritz and Harlequins, and over both Leinster and Ulster in the PRO12.
"We have been aware of Leinster's interest in Mike for some time," explained Sears.
"It is disappointing they have persistently targeted Connacht players in recent years, particularly when often not in the best interest of Irish rugby."
Connacht recently strengthened its playing squad with the arrival of experienced professionals like Dan Parks and Nathan White, who together with existing senior players have assisted the development of a crop of talented indigenous young players.