Last time out in the Magners League, Deasy impressed playing on the wing but prior to that had worn the number 15 jersey against Connacht when he scored a try.
The Corkman made his Heineken Cup debut as a replacement last weekend in San Sebastian, and is one of eight changes in personnel to the side that lost to Biarritz Olympique.
Lock Mick O'Driscoll misses out with an ankle injury as does hooker Jerry Flannery, while veteran prop John Hayes is rested, giving Tony Buckley the opportunity to impress from the kick-off.
Peter Stringer will start at scrum half, with Damien Varley joining Buckley and Marcus Horan in the front row.
Billy Holland gets the nod to replace O'Driscoll in the second row and Nick Williams and Niall Ronan come in for Alan Quinlan and James Coughlan in the back row. David Wallace shifts from openside flanker to number 8.
A late enforced change, due to a reccurence of Keith Earls' groin strain, will see Lifeimi Mafi moving into midfield to partner Jean de Villiers at centre, and Tom Gleeson lining up on the left wing.
Speaking ahead of Sunday's decisive encounter with the Blues, Munster team manager Shaun Payne said: "Wednesday was a case of refocusing and trying to be professional from the management and players' point of view.
"It was therapeutic for the guys to get back on the training pitch and not to dwell too long on what transpired (against Biarritz) last Sunday.
"There is still everything to play for. It's a play-off situation which we quite enjoy. We're not in it yet and obviously there are a couple of permutations but we need to ensure that we perform against Cardiff.
"The lads are definitely not wishing that their season was as good as over. We're up for this competition - we couldn't stand a double disappointment.
"We need to be competing in the Magners League. The gap between the Magners League and the Heineken Cup has definitely been closing and especially with the play-off system in place this year, there is a lot of added excitement."
A point on Sunday will see defending champions Munster through to the semi-finals if, in the process, they can restrict Cardiff to the minimum.
But Tony McGahan's men could still conceivably earn a home semi-final if they were to gain a five-point return and other results went their way.
MUNSTER (v Cardiff Blues): Scott Deasy; Denis Hurley, Lifeimi Mafi, Jean de Villiers, Tom Gleeson; Ronan O'Gara (capt), 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.