The enforced change sees England Sevens winger Anthony Elliott replace Samoan international David Lemi on the left wing. Lemi has had to return home due to an illness in the family. The two tactical changes are both in the pack where Alex Clarke replaces Darren Crompton at loosehead and Alfie To'oala replaces Joe El Abd at openside flanker.
The rest of the side remains unchanged as Bristol enter the game knowing that they need to win the game with a bonus point in order to have any chance of progressing to the knock-out stages.
Richard was realistic about the task ahead when he spoke to the media ahead of the game: "We've still got a mathematical chance of going through and the players are ready and all pumped up for it. It should be a fantastic game and a fantastic occasion.
"We're the outsiders. I think Stade Francais and Cardiff are probably the favourites but we could surprise everyone at the end, you never know. There's a huge incentive for us.
"David Lemi is unavailable as he's had to fly home so Anthony Elliott will come in. Anthony came in and did a great job against Wasps so we have no problem with bringing him in. But everyone else has been declared available from last weekend.
"We'll need to concentrate and keep our discipline. We didn't do that at Cardiff and conceded three late tries. They keep going and going and wear you down. They'll keep running the ball at you and your defence has to be absolutely spot on for 80 minutes."
"But the Memorial Stadium will be packed, it's a big game against a relatively close rival so it should be a great way to finish the group."
The Blues require two points to reach the quarter-finals for the first time since 2000-2001.
Dai Young's men recorded an important home win against Harlequins at the Arms Park. And they will travel across the Severn Bridge determined to show they can cope with the pressure at the Memorial Ground.
Bristol Rugby: L Arscott; T Arscott, R Higgitt, N Brew, A Elliott; J Strange, B O'Riordan; A Clarke, M Regan, J Hobson, R Winters, S Hohneck, M Salter (Capt), A To'oala, A Blowers
Replacements: S Linklater, D Crompton, G Llewellyn, J El Abd, G Beveridge, D Hill, S Cox
Cardiff Blues: B Blair; J Roberts, T Shanklin, G Thomas, J Robinson; N MacLeod, J Spice; G Jenkins, G Williams, T Filise, D Jones, P Tito, M Molitika, M Williams, X Rush (Capt)
Replacements: G Powell, T Thomas, S Morgan, M Lewis, R Rees, R Jones, T Selley
Referee: Alain Rolland (Ireland)