Sean O'Brien's season hangs in balance with Luke McGrath struggling to return for Scarlets showdown
Shoulder problem could require operation as Leinster fret on McGrath fitness for Scarlets
Seán O'Brien's season could be over after the Leinster flanker aggravated his shoulder injury on his return to action against Treviso last weekend.
The Lion has endured a disrupted campaign since injuring his hip in the pre-Christmas win over Exeter Chiefs, hurting his shoulder on both attempts to return.
It had been hoped that last week's game would see him prove his fitness for the European Champions Cup semi-final against Scarlets at the Aviva Stadium on Saturday, but he was carrying his left arm from an early stage and was taken off at half-time.
Although Leinster maintained O'Brien was 50/50 to play this weekend, the province have sent him for scans to establish if an operation is needed and surgery would bring a disrupted season to a close.
He has managed just 67 minutes since the turn of the year, hurting his shoulder in March on his comeback against Scarlets and again last Saturday. Having missed the Grand Slam, the Tullow native is now set to miss out on Ireland's summer tour of Australia.
With Rhys Ruddock sidelined and Jack Conan struggling with a knee problem, O'Brien's absence is a real blow to Leo Cullen's side ahead of the semi-final and is likely to see Scott Fardy continue at blindside flanker.
That could be exacerbated if Luke McGrath fails to recover from his ankle problem in time for the Scarlets clash.
The scrum-half is struggling to make it back for the game, meaning winger James Lowe could be squeezed out of the selection to make room for Jamison Gibson-Park at No. 9 due to the tournament rules around overseas players which mean only two of Fardy, Lowe and Gibson-Park can be selected.
Robbie Henshaw's return to fitness may see Isa Nacewa redeployed to the wing.
Munster, meanwhile, hope to have Keith Earls available but are sweating on the fitness of Jack O'Donoghue ahead of their clash with Racing 92.