Leinster say Jordan Larmour requires further tests to ascertain the severity of his ankle injury.
He suffered the injury midway through the first half of Leinster’s win over the Cell C Sharks on Saturday.
Rhys Ruddock, Luke McGrath and Ryan Baird will all observe the return to play protocols after sustaining head injuries in the game at the RDS.
James Lowe, Hugo Keenan, Ciaran Frawley and Ronan Kelleher all remain sidelined for this weekend’s meeting with Connacht.
Meanwhile, Leinster have signed former Saracens and London Irish hooker Tadgh McElroy on a short-term contract.
Ulster say Ian Madigan requires a scan on a knee injury he suffered in Saturday’s win at home to the Ospreys.
Kieran Treadwell will miss this weekend’s game away to the Emirates Lions with a chest injury.
And Marty Moore is going through the return to play protocols having sustained a concussion on Saturday night.
