Last time out in the Magners, Deasy impressed playing on the wing but prior to that had worn the number 15 shirt against Connacht when he scored a try and also made his Heineken Cup debut as a replacement last weekend in San Sebastian.
Mick O'Driscoll misses out with an ankle injury as does Jerry Flannery, while John Hayes is rested giving Tony Buckley the opportunity to impress from the off.
A point will see Munster through to the semi-finals if in the process they can restrict Cardiff to the minimum but they could still conceivably earn a home semi if they were to gain a maximum points return and other results went their way.
Munster: Scott Deasy, Denis Hurley, Keith Earls, Jean de Villiers, Lifeimi Mafi, Ronan O'Gara, Peter Stringer, Marcus Horan, Damien Varley, Tony Buckley, Donncha O'Callaghan, Billy Holland, Nick Williams, Niall Ronan, David Wallace. Replacements: Mike Sherry, Dave Ryan, Alan Quinlan, James Coughlan, Tomas O'Leary, Paul Warwick, Danny Barnes.