Darren Yapp will be making his first start of the season for Connacht coming back from long term injury. The outside centre missed just one game last season. Mostyn was out for the past two games after suffering an injury just a minute into the game against Cardiff.
David Slemen and Conor McPhillips will not be risked for the game having sustained injuries in last Saturday's bonus point win away to the Celtic League champions. Yapp will come into centre in place of James Downey who will move to the bench. Niall O'Brien will start on the wing instead of McPhillips and Mostyn will take over at full back from Slemen.
The front eight will be unchanged for the game with Bernard Jackman poised to make a return from injury taking a place on the bench.
Saturday will mark Counties of Connacht jersey day'. Anyone wearing a county jersey of Mayo, Galway, Roscommon, Sligo or Leitrim will be admitted for free to Saturday's game.
Connacht: Matt Mostyn; Ted Robinson, Darren Yapp, Mark McHugh, Niall O'Brien; Paul Warwick, Conor O'Loughlin; Ray Hogan, John Fogarty, Stephen Knoop, Andrew Farley, Pieter Myburgh, Michael Swift, Matt Lacey, Mick Carroll.
Replacements: Bernard Jackman, Adrian Clarke, Christian Short, John Muldoon, Mike Walls, Eric Elwood, James Downey.