Warren Gatland believes it will be "a big psychological boost" if Wales finish top of their World Cup group.
The Six Nations champions are halfway there following victories over Georgia and Australia.
If Wales beat Fiji in Oita on Wednesday, it guarantees a quarter-final place, and a win against Uruguay four days later would confirm they head Pool D.
"If you win the group, it's a big psychological boost because you are playing a quarter-final against a team who would have lost a game in their pool," Wales head coach Gatland told WRU TV.
"I think psychologically it's quite important for us to win this group, win the next two games, and then to start thinking about our quarter-final opponent.
"We are pretty happy with two from two. The next two matches are very important.
"Fiji are going to be tough for us. They had a great performance against Georgia. They are very much a confidence side, so we will have to be on top of our game and be defensively strong at the set-piece.
"We've got a short turnaround of four days, so a lot of the players who haven't had any rugby will get an opportunity then. They will be chomping at the bit to play against Uruguay.
"We've refreshed nicely since the Australia game, and the guys are really looking forward to the opportunity against Fiji."
Biggar followed up an impressive performance against Georgia by starring in the Australia game before he went off in the first half following a try-saving tackle on Wallabies centre Samu Kerevi.
Biggar failed a head injury assessment, but Patchell took over in style, kicking 14 point as Wales closed out a thrilling 29-25 win.
"It's brilliant, absolutely brilliant," Jones said.
"You look at the talent they both have, the mental toughness they have, it's great. We are in a fortunate position.
"Dan has been an absolute credit. These guys are open-minded, they are evolving and improving all the time.
"That's the mindset you've got to have. Looking at their work ethic, determination and will to improve, it's a pleasure to work with them.
"I just think we are blessed. From my end, to go out on the paddock and work with those guys, when you've got a group driving each other all the time, that's what you want.
"You have got to give Rhys a huge amount of credit. He has put a lot of time in with Neil Jenkins (Wales' skills and kicking coach) as well.
"He has worked hard on his game, and it was wonderful to see that transfer to the pitch against Australia. To go on and do what he did, he deserves a huge amount of credit.
"Rhys is getting the line moving, his game-management as well, that drop-goal (against Australia). They are key moments to keep the scoreboard ticking over. It's smart rugby."
Former Wales number 10 Jones is well aware of Fiji's threat – he played in the 2007 World Cup game that Wales lost in Nantes, which meant a pool-stage exit.
"We have to play our way," he added. "We know our game plan going into this game, and it is about delivering that.
"It's a mental challenge, but the players are confident about how they are practising.
"We respect Fiji, and rightly so. From a personal perspective, I am fully aware of how good they are.
"We have got to make sure from an attacking element that when we have got the ball we keep the ball.
"It (2007) highlighted what Fijian rugby is all about.
"Give them space and time and they move the ball well, have an off-loading game and put you under pressure. They did that day and scored some wonderful tries."