Scotland head coach Vern Cotter claims his side will be the underdogs when they host Tonga tomorrow.

The Dark Blues have home advantage for the Rugby Park clash as well as the bragging rights when it comes to the current IRB Rankings - with four rungs separating the eighth-placed Scots from their weekend guests.

But despite two encouraging displays over Argentina and New Zealand, Cotter thinks the Pacific Islanders are the favourites to win the final autumn Test in Kilmarnock.

The Sea Eagles have beaten Georgia and the USA in their last two outings - while the very mention of Tonga is still enough to make several members of the Scots squad shudder following their mortifying 21-15 loss in Aberdeen two years ago.

"That match has been talked about," said Cotter, who took over in the summer. "I know the players were disappointed with that result two years ago. There is a quiet determination among them to play well.

"Tonga are a better team than they were then. They almost come into the match as favourites. They have won their last two games and beat Scotland two years ago.

"We know it will be difficult. We haven't viewed the footage of that match two years ago but we know their players individually and are very aware of what they have done in that last two games.

"Beating Georgia is very hard and they put 40 points on the States. Their game plan has evolved.

"Because of the park and because of the opposition, this match will be different to the ones against Argentina and New Zealand. We will have to adapt."

The match will be the first major Test to have ever been played on a synthetic surface.

But Kilmarnock's plastic pitch is not the only thing concerning Kiwi coach Cotter.

"We have spoken about the fact this could be the danger game. It was easy for the guys to get themselves up for Argentina because it was the first game of the series and then the All Blacks.

"But now we have shifted away from Murrayfield and changed the environment.

"At the same time, though, I think the guys are enjoying having to prepare for another game away from home as we will have to at the World Cup.

"There is an opportunity to prepare well and execute well in a difficult situation, so mentally we will have to be resilient. It will be fascinating to see how we deal with it."

Injuries have forced the Dark blues boss into four changes.

Tight-head prop Geoff Cross and number eight Johnnie Beattie come into the pack for Euan Murray and Adam Ashe, who miss out through thigh and neck injuries respectively.

In the backs, 90-cap Glasgow Warrior Sean Lamont replaces club-mate Mark Bennett after the centre was ruled out for 12 weeks with a hamstring tear, while Edinburgh wing Tim Visser makes his first appearance since the summer tour in place of the injured Sean Maitland, also ruled out by a hamstring strain.

But Cotter has warned the newcomers that the men they are replacing have set the bar high.

He said: "The guys who have played have done well. They are setting standards within the group, so we didn't want to change it too much.

"But injuries give the guys coming in a chance. The natural competitors in them will show through, though.

"They realise the guys carrying the jersey in the two previous games have played well but they now have a chance to stake a claim.

"Obviously they have the Six Nations coming up but there is also the World Cup not far away so I'm sure they will have that in the back of their minds."

Cotter's men will get their first look at the Killie's 3G surface on Friday morning but the head coach does not see astroturf surfaces becoming the norm on the international stage.

Instead, he reckons the kind of hybrid surface recently installed at BT Murrayfield will become more and more popular with the top nations.

He said: "When you look what has been done at Murrayfield with a combination of the two types of pitch, that seems to be the best answer.

"The Aviva in Dublin has it as well and I think that is where we are heading. Like anything, a combination of two good ideas works best."