The bench includes Academy player Cian Bohane and Garryowen hooker James Rael for the first time. Peter Borlase has also been selected after recovering from a back injury.
In the new cup format this season, Munster 'A', placed in Pool 2, are pitted against opposition from Pool 1 including English sides Cornish Pirates and Moseley, Welsh outfit Neath and Scottish club Ayr.
Saturday's game is a 'must win' affair as Costello's charges currently lie in second place in the pool with five points, and Cross Keys hold pole position on ten points.
Ayr, like Saturday's hosts, have recorded one victory and one defeat at this stage and for any chance of progressing in this competition Munster 'A' need to secure a home victory this weekend in Kerry.
"We got ourselves into a situation unfortunately, by losing to Cornish Pirates, that our group is pretty competitive so we're probably going to need two wins out of the last two games to qualify," explained Costello.
"We were happy with our performance against Pirates but we were a bit unlucky towards the end, we should have put the game beyond a doubt earlier on so it's our own fault that we're at this stage.
"We had a good performance against Neath and an extra week together so it's our third week together now and we'd hope for an even more improved performance on Saturday.
"Ayr are one of the most competitive Scottish sides every year, they had a very good win against Plymouth who are a good Championship side and we're expecting another high standard match this weekend.
"From our point of view at this stage we've to focus very much on ourselves, making sure we just improve on the past performances."
Commenting on the fact that the game is being held at Tralee RFC, he added: "I suppose the only comparison I have is the pre-season training that we had down there (in Tralee).
"They were fantastic hosts, with fantastic facilities, and what was really pleasing that day was how good and big the crowd was. With the Heineken Cup match on afterwards, Tralee are making a massive effort to create a real atmosphere and event down there.
"We're hoping that we get a good crowd, it's a massive difference and that's why we brought games out of Musgrave Park and Thomond Park where you wouldn't even notice five or six hundred there.
"We've had good games in the past in Clonmel and Waterford and we're really looking forward to our first game in Tralee, and if they are as supportive as they were for the training day it will be fantastic."
Tickets will be available at the gate and are priced at €10 for adults, €3 for children and €20 for a family pack (two adults and two kids).
Further match details are available here.
MUNSTER 'A' (v Ayr): Sean Scanlon; Luke O'Dea, Tom Gleeson, JJ Hanrahan, Ronan O'Mahony; Declan Cusack, Duncan Williams; David Kilcoyne, Duncan Casey, Christy Condon, Dave Foley, Ian Nagle, Billy Holland (capt), Tommy O'Donnell, Paddy Butler.
Replacements: James Rael, Peter Borlase, David O'Callaghan, Brian O'Hara, Cathal Sheridan, Cian Bohane, Corey Hircock.