Bundee Aki has been ruled out of Connacht's crucial United Rugby Championship meeting with Ulster at the Aviva Stadium (5.15pm).
The 31-year-old has suffered a knee injury, although is expected to be back in full training with Ireland next week.
Aki's knock means Tom Daly comes into the centre following last week's defeat to Munster at Thomond Park, among three changes to Andy Friend's side.
Kieran Marmion returns to the starting team in place of Caolin Blade, partnering Jack Carty, who once again captains the side.
Meanwhile, Eoghan Masterson makes his first start of the season, taking the place of the injured Cian Prendergast in the back row.
Out-half Conor Fitzgerald is included on the bench, with Connacht reverting back to a 5:3 split.
The western province come into the game 14 points behind league leaders Ulster, who have secured maximum points from their opening four games.
Dan McFarland's side are also boosted by the return of captain Iain Henderson (below), who makes his first appearance of the season.
The 29-year-old had thumb surgery following the British and Irish Lions tour, but comes into the team to partner Alan O'Connor in the second row.
Irish internationals Robert Baloucoune, Stuart McCloskey and Eric O'Sullivan also return from injury for Ulster, with Baloucoune taking the place of the injured Will Addison, McCloskey starting in place of Stewart Moore, and O'Sullivan replacing Andrew Warwick who is named on the bench.
Teenage scrumhalf Nathan Doak continues to deputise at scrum-half in place of the injured John Cooney
Connacht: Tiernan O'Halloran; John Porch, Sammy Arnold, Tom Daly, Mack Hansen; Jack Carty (capt), Kieran Marmion; Matthew Burke, Dave Heffernan, Finlay Bealham; Niall Murray, Ultan Dillane; Eoghan Masterson, Conor Oliver, Paul Boyle
Replacements: Jordan Duggan, Shane Delahunt, Jack Aungier, Oisin Dowling, Jarrad Butler, Caolin Blade, Conor Fitzgerald, Diarmuid Kilgallen
Ulster: Ethan McIlroy; Robert Baloucoune, James Hume, Stuart McCloskey, Craig Gilroy; Billy Burns, Nathan Doak; Eric O'Sullivan, Rob Herring, Tom O'Toole; Alan O'Connor, Iain Henderson (capt); Matty Rea, Nick Timoney, David McCann
Replacements: Brad Roberts, Andrew Warwick, Ross Kane, Kieran Treadwell, Greg Jones, David Shanahan, Mike Lowry, Ben Moxham.
Conor Murray and Damien de Allende are both set for their first appearances of the season off the bench in tomorrow's URC trip to the Ospreys (7.35pm, live on RTÉ2 and RTÉ Player)
The pair are included on a powerful replacements bench which also contains Gavin Coombes, Ben Healy and Keynan Knox.
Johann van Graan has made eight changes to his side as they look to maintain their 100% start. Jack Crowley is given his first start of the season at out-half, with the 21-year-old named alongside Craig Casey in the half-backs.
Peter O'Mahony switches position to openside flanker, and is joined by Tadhg Beirne, who moves from the second to back row, with the pair either side of Jack O'Donoghue.
Matt Gallagher, Liam Coombes, Dan Goggin and Shane Daly are also brought into the backline, while Jeremy Loughman and Fineen Whcherley come into the pack.
Munster: Matt Gallagher; Andrew Conway, Liam Coombes, Dan Goggin, Shane Daly; Jack Crowley, Craig Casey; Jeremy Loughman, Niall Scannell, John Ryan; Jean Kleyn, Fineen Wycherley; Tadhg Beirne, Peter O'Mahony (capt), Jack O'Donoghue.
Replacements: Kevin O’Byrne, Josh Wycherley, Keynan Knox, Gavin Coombes, John Hodnett, Conor Murray, Ben Healy, Damian de Allende.
Follow Connacht v Ulster (Saturday 5.15pm) and Ospreys v Munster (Saturday 7.35pm) via our live blogs on rte.ie/sport and the RTÉ News app. Watch Ospreys v Munster live on RTÉ2 and RTÉ Player.