Ireland will be without flanker Josh van der Flier for their tour of South Africa, while wing Simon Zebo is a doubt due to injury.
Van der Flier, who made his international debut in this year's Six Nations, underwent ankle surgery this week and faces eight weeks on the sidelines.
The 23-year-old will therefore miss Leinster's Pro12 semi-final against Ulster on May 20, in addition to the final should his team progress, and Ireland's three Tests in South Africa.
Zebo's domestic season is also over after the Munster back had keyhole surgery on his knee.
A Munster statement read: "A return timeline will be reviewed once initial post-op healing is complete."