Leinster's Luke Fitzgerald will undergo surgery to correct a persistent neck injury.
As a result, the 24-year-old will now miss the Heineken Cup final and Ireland's summer tour of New Zealand.
"Obviously to lose a player of Luke's pedigree at such a crucial time of the season is a massive blow, not just for the team and our supporters but also for the player himself," said Leinster head coach Joe Schmidt.
"Luke has been in fine form recently and as well as his capabilities on the field, he is a positive and popular presence within the dressing room.
"Knowing Luke, he will be determined to overcome this setback and aggressively tackle his rehab to regain full fitness and he will continue to benefit from the full support of Leinster Rugby and the IRFU during that time frame."
Fitzgerald failed to make the Ireland squad that was selected for last year's World Cup.
