'Ikale Tahi rugby coach Toutai Kefu says this afternoon's blockbuster test against Fiji in Nuku'alofa is "like a grand final" for his side.
Tonga remain in the hunt for one of two automatic Rugby World Cup qualifying berths after beating Manu Samoa at Teufaiva Stadium last weekend.
Fiji are coming off impressive victories against Italy and Scotland in Suva and will seal top spot in Oceania, and a more favourable World Cup pool, with victory this afternoon.
But Toutai Kefu said the hosts are improving and won't be lacking in motivation.
"They still play with that Fijian flair. They're very athletic, they're big. Their set piece is a strength of theirs, it's no longer a weakness, so they're going to be a massive challenge - we don't doubt that - but we still need to just keep chipping away at our own game."
"It will still be more about us than it is about them so we just need to tighten a few things up, make better decisions but it's a massive challenge. The position we're in, the underdog status I think really suits us and we've just got to have that belief."
Tonga are bottom of the Oceania qualifying group and need at least a bonus point against Fiji to have a chance at direct qualification, with Samoa still to host the Flying Fijians next weekend.
"If we secured a automatic selection into the Rugby World Cup definitely that first position gets us into a better pool so we definitely want to win and win well but, I think, looking at it the team that doesn't qualify goes through to the playoff."
"If they secure a win there - I think it's a home and away (against a European team) that gets you into a pretty good pool as well so it could be a win-win either way."
Flying Fijians coach John McKee said locking up the Oceania One qualifying berth is key target for them but they also have silverware to defend.
"Pool D is a much better pool to be in than Pool C, so that's always hovering in the background but we are holders of the Pacific Nations Cup and we want to continue our number one status across the Pacific," he said.
"If they manage to beat us this weekend they would be Pacific Nations champions but (we're) definitely not really considering that possibility."
With Patrick Osborne and former sevens star Josua Tuisova out wide, John McKee admits Fiji's game plan is no secret.
"We'll be looking to get the ball to the wider channels and put a lot of pressure on Tonga that way."
"That's our objective, Tonga will be obviously going out to stop that occurring so the important thing for us is to be able to impose our game and not get too caught up in a war of attrition."
Sonatone Takulua was a standout for Tonga in their tests against Wales and Samoa and John McKee said they'll be looking to put plenty of pressure on the half-back area.
"We know they'll bring a very physical approach to the game. They'll play off their halfback a lot to win some go-forward before they chance their arm and go wide, so we're going to have to be very strong in our defence around near the edges of the ruck and around their inside backs because that's where they're going to come at us to try and gain some ascendancy," he said.