Cardiff Blues travel to Parc y Scarlets on Friday for a must-win clash with Scarlets in their final regular season match.
The Blues need to win to guarantee qualification for the last four, but have not won away from home on Welsh soil so far this season.
It is also a must win match for the Scarlets to give them any hope of reaching the Magners League semi-finals.
The hosts' last home fixture of the season at Parc Y Scarlets is expected to attract a five-figure crowd as the nail-biting finish to the league concludes with the Scarlets, Blues and Ospreys all still able to secure a play-off place. This will be the first time all the final sixth round matches are played at the same time.
Having kicked off strongly in the league, the Scarlets spent 12 consecutive weeks in the play-off zone. The now sixth-placed Scarlets are reliant on other fixtures going their way but will want to finish on a high after a strong performance away in Glasgow with five tries, a bonus point win and qualification for Europe as one of the top placed three Welsh regions.
Cardiff Blues made a number of changes to their side. With wing Tom James picking up a groin injury at Rodney Parade last Friday and Leigh Halfpenny and Richard Mustoe out, Jamie Roberts moves to the wing with Dafydd Hewitt starting at centre.
In the forwards Sam Warburton moves to blindside with Martyn Williams starting at seven. Michael Paterson moves to the second row in place of the injured Bradley Davies while Sam Hobbs starts in the front row in place of the injured John Yapp.
John Yapp picked a calf injury in the loss to the Dragons, while Davies is expected to be out for between two to six weeks with a chest injury
The Blues will be looking to reverse the round six loss to the Scarlets who won 16-10 at Cardiff City Stadium.
"Obviously we were disappointed with the result at the Dragons, however, there were some positives which we've looked at and have to build on," said Cardiff Blues Director of Rugby David Young.
"We are still fourth, so we know what we have to do. We have to go there and win, it's a difficult place to go to, we know that, but at the end of the day if you want to get into the top four you have to go to these places and win."
"We are well capable of winning and have to be upbeat."
"If we win we will be in the Play Offs which was our aim at the start of the season, then you are in one-off games where anything can happen."
"Everyone has injuries at this stage of the season. It's nice if you can play with your best team, but if you can't you just have to role your sleeves up and get on with it."
Meanwhile, Wales and Scarlets fly-half Stephen Jones takes the helm again in the pivotal role at 10, with Morgan Stoddart at full-back, George North and Scotland international Sean Lamont on the wings, Regan King and Scott Williams in centre partnership and Tavis Knoyle starting at scrum-half. Supporters will bid a fond farewell at Parc y Scarlets to Kiwi magician Regan King after six years in a Scarlets shirt.
"All we are focusing on is the win; mathematically we still have a chance to go through but that's not in our control," said Head Coach Nigel Davies.
"The key is we want to finish our season on the right note and with the right momentum. Our last result in Glasgow showed the progression we've made, there was a lot of pressure on us to get that win and we controlled the game well in the second half and played with composure.
"It's going to be a big ask against a physical Blues side full of internationals and they will be bitter after their loss to the Dragons. They're in the driving seat in that if they win they will qualify so it's going to be a big local derby game with both teams wanting to finish on a high."
Stephen Jones said: "It's going to be interesting with different styles of play at work and it'll be a good challenge for both sides. We watch the Blues all season, so we know what a good side they are, they have some key players and regardless of their last result they'll come here expecting to win. We have to focus on our game and keep our house in order.
"It's going to be a big Welsh derby against a very good side, the atmosphere will be great and the players know each other well. The Blues play a good brand of rugby and if the sun's shining it will make for an exciting, open game and a great way to conclude the season."
Form: Scarlets won 16-10 at Cardiff City Stadium in round six and are going for a first season's double over the Blues since 2008/09. Scarlets must win to give themselves any hope of reaching the Magners League semi-finals, but even that may not be enough if other results conspire against them. Scarlets 21-15 victory over Dragons the last time they hosted a fellow Welsh region ended a four game losing run at Parc y Scarlets against other Welsh regions. The Blues also need to win to guarantee qualification for the last four, but have not won away from home on Welsh soil so far this season.
Scarlets: 15 Morgan Stoddart, 14 George North, 13 Regan King, 12 Scott Williams, 11 Sean Lamont, 10 Stephen Jones, 9 Tavis Knoyle, 8 Ben Morgan, 7 Johnathan Edwards, 6 Rob McCusker, 5 Dominic Day, 4 Lou Reed, 3 Rhys Thomas, 2 Matthew Rees (c), 1 Iestyn Thomas.
Replacements: 16 Emyr Phillips, 17 Phil John, 18 Peter Edwards, 19 David Lyons, 20 Richie Pugh, 21 Martin Roberts, 22 Rhys Priestland, Lee Williams.
Cardiff Blues:15 Dan Fish, 14 Jamie Roberts, 13 Casey Laulala, 12 Dafydd Hewitt, 11 Chris Czekaj, 10 Dan Parks, 9 Richie Rees, 8 Xavier Rush, 7 Martyn Williams, 6 Sam Warburton, 5 Paul Tito (c), 4 Michael Paterson, 3 Taufa'ao Filise, 2 Gareth Williams, 1 Sam Hobbs.
Replacements: 16 Rhys Williams, 17 Tom Davies, 18 Scott Andrews, 19 Deiniol Jones, 20 Ma'ama Molitika, 21 Lloyd Williams, 22 Ceri Sweeney, 23 Harry Robinson.
Date: Friday, May 6
Venue: Parc y Scarlets
Kick-off: 19:05 BST
Referee: Nigel Owens (WRU)