Sherry has three Heineken Cup appearances off the bench to his credit all from last season, while O'Donnell's only appearance at this level was when he replaced James Coughlan during Munster's pool win over the Scarlets at Thomond Park back in December.
There are two changes in the backs division where Murray and Denis Hurley, who is also back from injury, come in for the benched Tomas O'Leary and Johne Murphy respectively.
Up front Wian du Preez starts his seventh consecutive Heineken Cup match at loosehead prop, and the fit-again Ryan and O'Connell resume in the second row.
In the back row, Peter O'Mahony switches from openside to blindside flanker and O'Donnell is preferred to David Wallace who will hope to have an impact off the bench.
Asked about Munster's progression with their scrum and lineout, McGahan said: "The foundations are there (for a good set piece) and if you look at our ERC pool games when this group was last together over 10 weeks ago, we had some strong formations and the set-piece was part of that.
He added: "We have been immensely impressed with the direction Ulster have taken, especially from where they were a couple of years ago.
"When you look at where they are at this point and see where they have come from and the build-up from last year. The commentary this week from their senior players has alluded to that.
"They are not happy with just making the quarter-finals, they really see this as an opportunity to work their way further.
"I think Brian (McLaughlin) and his coaching staff and certainly David Humphreys at the top of that tree have done a fantastic job at gathering the players, giving the confidence, support and coaching to contribute to what is a really strong package."
MUNSTER (v Ulster): Felix Jones; Denis Hurley, Keith Earls, Lifeimi Mafi, Simon Zebo; Ronan O'Gara, Conor Murray; Wian du Preez, Mike Sherry, BJ Botha, Donnacha Ryan, Paul O'Connell (capt), Peter O'Mahony, Tommy O'Donnell, James Coughlan.
Replacements: Damien Varley, Marcus Horan, Stephen Archer, Donncha O'Callaghan, David Wallace, Tomas O'Leary, Ian Keatley, Johne Murphy.