The Fijians, who have lost to England and Australia in Pool A, will be without suspended winger Nemani Nadolo and injured scrumhalf Nikola Matawalu for the game in Cardiff on Thursday (local time).
"We've selected the strongest team we can for the type of game we need to play," McKee told reporters on Wednesday.
"Only one player was out of contention and that was Nikola Matawalu, who has a bruised back."
McKee said the loss of the giant Nadolo was not a problem.
"It hasn't hindered our preparation," the New Zealander said.
"We're very strong in the back-three area and we've got very good players coming into the team to cover his position, and also Waisea Nayacalevu who got injured in our last game.
"The wing/fullback area is a very strong area for us and the guys that are playing tomorrow are well capable of the task and are very good players."
He added that Wales may not know what to expect in the absence of Nadolo.
"They can think what they like but maybe there are some players there that they are not so familiar with, so they may not quite know what to expect," McKee said.
McKee was impressed by the resilience Wales showed to beat England 28-25 at Twickenham.
"Firstly, looking at their game last week, you can see how strong mentally the Welsh team were," he said.
"They hung into the game, they never gave up and showed great spirit to get the win.
"At the same time, they would have put a lot of emotional energy into that game and that's the question for them - can they get back up again after a short turnaround?"
Fiji captain Akapusi Qera is expecting a Welsh onslaught.
"We know that the Wales team are coming after the victory against England," he said.
"We know that they will be fired up as well and the motivation for the boys is to try and make ourselves proud and reward ourselves for all the hard work of the last few weeks."
