Scotland head coach has said that he needs all 31 of his players fit if they are to progress to the quarter-finals of the Rugby World Cup.

Cotter has made 10 changes to the lineup that beat Japan, as he expects a physical confrontation with USA.

"We said from the start that we would need the whole group of 31 players for this campaign," Cotter told Scotland Rugby's official website. "We have known this schedule for a long time and have tried to keep continuity in selection, while also introducing fresh legs to what will be another very physical challenge this Sunday.

"I was pleased with both the commitment and composure against Japan, particularly towards the end of the game, however we are always working and looking for things on which to improve.

"Hopefully we will see the result of that this Sunday in another very important Test match in our pool."

Captain Greig Laidlaw has dropped to the bench, with Henry Pyrgos coming in to replace him as both scrum-half and skipper.