The request is believed to have been made on the basis of some player's religious convictions although Ulster have played both League and Heineken Cup games in the recent past on Sunday's.
Nor does Irwin expect that religious convictions will preclude them traveling without full support, their followers expected to take up their full 6,000 ticket allocation.
Meanwhile, those players not involved with national squads this week are on a week off. The squad re-assembles next Monday with a trip to Italy and games against Aironi and Treviso on the horizon.
Those games represent the start of a defining period as far as Munster are concerned in the RaboDirect PRO12. During the RBS Six Nations window, they play five RaboDirect PRO12 games, four of which are away from home.
That League period concludes with a home tie against Leinster, one week before they take on Ulster in the Thomond Park Stadium quarter final.