Duffy missed last weekend's record league defeat at Cardiff due to a quad muscle strain, while Matthews was sidelined by a shoulder injury.
Troy Nathan has also been recalled with Andy Dunne ruled out with a hamstring injury.
Hooker Adrian Flavin (ribs), flanker Ray Ofisa (shoulder) and scrum half Conor O'Loughlin (hip) are the westerners' other injury concerns.
Meanwhile, the Connacht Branch have confirmed that they will have a second car park at Galway Community College, Moneenageisha, available for the Connacht v Leinster match.
Signage will be placed at both sides of the Moneenageisha roundabout directing cars to this car park.
This car park will opens from 4.30pm next Sunday and will close one hour after the final whistle.
CONNACHT Squad (v Leinster): Backs (10) - Liam Bibo, Kieran Campbell, Fionn Carr, Gavin Duffy, John Hearty, Ian Keatley, Keith Matthews, Frank Murphy, Troy Nathan, Mike Roberts.
Forwards (12) - Andrew Browne, Sean Cronin, Andrew Farley, Ronan Loughney, Mike McCarthy, Robbie Morris, Conor Muldoon, John Muldoon, Johnny O'Connor, Colm Rigney, Michael Swift, Brett Wilkinson.