Munster picked up a signature Champions Cup win as they downed Saracens 17 - 12 in an old school tussle at Thomond Park.
There is no return for O’Mahony, whose last appearance came in the December 13 defeat at Castres.
Ahead of the highly anticipated URC matchup between Leinster and Munster, both teams have welcomed back multiple players to their starting lineup.
A hat-trick of tries from Tom Farrell saw Munster win a scrappy opening Irish interprovincial of the festive season 22-19 over Ulster at the Kingspan Stadium.
Veteran scrum-half Conor Murray has returned home to Ireland midway through Munster's tour of South Africa for personal reasons.
The veteran back-rower and tighthead Oli Jager were starters in last Saturday’s rain-sodden win over Ospreys.
World Cup-winning Springbok Jean Kleyn is poised to make his return to action for the first time since November last year after recovering from an eye injury.