The Blues' unbeaten Super 14 rugby record goes on the line on Sunday, when they play the Sharks in steamy Durban, with coach David Nucifora expecting their undefeated hosts to turn up the heat.

"It seems everybody is talking us up and them down, but the bottom line is that the Sharks also have three wins from three," Nucifora said.

"They are coming off a good win at Loftus Versfeld (29-15 over defending champions the Bulls) and wins there are hard to come by.

"I would agree that the Sharks have not yet hit their best form, but they will be looking to this match to show a big improvement.

"And with us very keen on finishing our tour unbeaten, it is shaping up to be one heck of a game."

Sharks coach Dick Muir agreed it would be a big test for both teams, adding his players were keen to shake off their early season sluggish form.

"We will see how good the Blues really are and we will see if we have what it takes to 'up' our game and play towards our potential.

"If we can do that, we would hope to win. If we continue the way we have been playing we will lose."

The Sharks will be without Springbok halfback Ruan Pienaar who has a collar bone injury and possibly rugged forward A J Venter but the ledger is evened out as the Blues will be without inspirational fullback Isa Nacewa (injured knee) whose replacement will likely be Ben Atiga.

New Zealand's other unbeaten side, the Crusaders take their road trip to the hot climes of Perth to play the Western Force, also on Sunday morning (NZtime).

The round four tie is the first of the home campaign for the Force after a bold start to the competition with two wins (Cheetahs and Lions) and a narrow loss (Sharks) from three outings on the road in South Africa.

John Mitchell's team will be looking to continue with the momentum gained at Subiaco where the Force won four from seven last season.

They will also take on a travel-weary Crusaders, whose arrival in Perth on Tuesday was preceded by 15 hours in the air.

Hovering in the background of this match is a predicted temperature of 37degC for match day.

The option exists for the game to be played in 20-minute quarters, and not the regular 40-minute halves, if the teams and match officials believe it is necessary.

Force playmaker Matt Giteau, is unbothered about impressing incoming Wallabies coach Deans -- the Crusaders coach -- and thought the match would be decided in his tussle between himself and All Black Dan Carter.

It would be a taste of things to come for the Wallabies and All Blacks in this year's Tri-Nations and Bledisloe Cup series.

"Both are thinking sides and obviously the two five-eighths will be pivotal," Deans said.

In other fourth-round matches, the Highlanders welcome back skipper Craig Newby as they seek their first win of the season on Friday in Dunedin, against a Hurricanes side missing star forwards Chris Masoe and Neemia Tialata as well as fullback Cory Jane.

And the Chiefs will be wanting to bounce back from their 39-19 pasting from the Hurricanes when they have the winless Cheetahs on their menu in Hamilton on Saturday.

Other offerings in the round include the Waratahs-Brumbies derby, the Reds playing the Stormers in Brisbane and the Bulls meeting the Lions.