Dragons wing Aled Brew starts in place of the injured Shane Williams (shoulder) and wins his fourth cap after last featuring on the international stage against England at Twickenham in 2007. Ospreys centre Andrew Bishop is reunited with his regional colleague James Hook, with Blues back Tom Shanklin moving to the bench.
Up front it's an all Ospreys front row with Huw Bennett taking up hooker duties from Scarlet Matthew Rees, who is rested. In the second row Ian Gough (Ospreys) and Deiniol Jones (Blues) lock the scrum, with Bradley Davies (Blues) moving to the bench and Alun Wyn Jones (Ospreys) rested.
In the back row Jonathan Thomas is retained alongside returning captain and fellow Osprey Jones, Dragons back row Lydiate faces a fitness race to replace veteran Blues flanker Martyn Williams. If Lydiate returns from ankle trouble in time Williams will sit out the Fiji match, but should the Dragon fail fitness testing this week Williams will win his 98th cap for Wales.
On The bench Tongan born 'Toby' Faletau (full name: Tangaki Taulupe Faletau) is set to be Wales' 1079th player.
"We must maintain our focus this week, if we even cast an eye beyond Fiji on Friday night, to the World Cup or even just to the game a week later we could be left counting the cost," said Gatland.
"We know all too well that the Fijians bring an extra dimension to their game when they face Wales and there is no doubt they will have targeted us this weekend as a game think they can win.
"We have been self critical this week about our failure to close out matches when the finishing line may be in sight, no less than was evident against South Africa on Saturday.
"We need to be ruthless against Fiji and, with a few changes made to the starting line-up, more organised than ever.
"A couple of players, like Richie Rees and Huw Bennett get their chance to show what they can do from the start of a game rather than off the bench.
"And on the bench too we have a wealth of experience to call upon, should we need it, alongside a young man originally from Tonga who now qualifies for Wales who, at just 20, is alread quite a prospect.
"We are giving Dan (Lydiate)'s ankle injury time to settle down and are looking for him to start in a young back row, if he doesn't make it Martyn (Williams) will come straight, but we are fairly relaxed about which way that falls and are blessed to be able to switch and change in that area if necessary to minimum impact."
WALES : Lee Byrne; George North, Andrew Bishop, James Hook, Aled Brew; Dan Biggar, Richie Rees; Adam Jones, Huw Bennett, Paul James, Ian Gough, Deiniol Jones, Ryan Jones (C), Dan Lydiate/Martyn Williams, Jonathan Thomas
Replacements: Richard Hibbard, John Yapp, Bradley Davies, Toby Faletau, Mike Phillips, Stephen Jones, Tom Shanklin