Team manager John Fallon said they were continuing the rotation policy which had served them so well this season, as they bid to nail down a quarter-final spot for the second year running.
Connacht take a 29-7 lead into the second leg but they expect a backlash from Pau.
'Pau have a record of turning around first leg deficits, we knew that before we played them last week. Their most notable one was last year when they lost 29-3 at Ebbw Vale and then proceeded to put 64 points on them in France.
'Pau have a 100% record at home this season and should have the likes of Imanol Hardinorduquy, Damien Traille and Garrick Morgan back for this one.
Everything indicates they will be fired up to have a right cut at us,' said Fallon.
Three of the changes are in the backline. Mark McHugh, forced to withdraw on Friday, having been selected for the first leg, returns and is selected at full-back.
Ted Robinson starts on the left-wing and Eric Elwood returns to partner Mike Walls at half-back. Up front, Damien Browne comes into the second row with Matt Lacey selected at openside wing forward. Paul Neville and Peter Bracken are among a number of players out through injury, while winger Wayne Munn was not considered for selection as his wife Julie is due to give birth to the coupleÂ¹s second child.
The winners of SaturdayÂ¹s tie will play either Narbonne or London Irish in the quarter-finals. London Irish take a 20-13 lead to Narbonne for Saturday eveningÂ¹s game.
Connacht (v Pau): M. McHugh; M. Mostyn, D. Yapp, T. Allnutt (capt.), T. Robinson; E. Elwood, M. Walls; D. McFarland, B. Jackman, A. Clarke; D. Browne, A. Farley; M. Swift, M. Lacey, J. O'Sullivan.
Replacements: J. Fogarty, W. OÂ¹Kelly, M. McCarthy, T. Carter, C. Keane, D. Hewitt, C. McPhillips.