Dean Ryan's Guinness Premiership leaders will make the trip to Harlequins with the former Otago Highlander in a new half-back combination alongside scrum-half Rory Lawson.
Walker slots in at stand-off because Ryan Lamb has slight bruising to his shoulder and Chris Paterson, who started against Bristol a fortnight ago, moves to the bench.
There are also returns for winger Lesley Vainikolo and full-back Iain Balshaw as Gloucester look to extend their five point advantage at the top of the table.
Walker will make his 10th appearance of the season in the Premiership tomorrow - his one try coming against Leicester back in September.
"Hopefully, we have learnt some lessons from the last time we had international players available," Ryan said, referring to the defeat against Bristol. "We suffered some basic problems then in terms of preparation and we are keen they don't happen again.
"Players needed to turn up on Monday and show me they wanted to be around and involved. There is no doubt we want to get on a bit of a run and find some form.
"We began that process by thinking our way out of some problems against Newcastle last weekend and we need to build on that tomorrow in what will be a very tough game."
Outside Lawson and Walker, Jack Adams and Anthony Allen continue their midfield partnership, while James Simpson-Daniel, who has 10 tries in 19 games in all competitions, will partner Vainikolo and Balshaw in Gloucester's back three.
Ryan has also made changes up front. Loose-head prop Nick Wood will make his sixth successive start and 17th in total alongside hooker Olivier Azam and tight-head prop Carlos Nieto.
Peter Buxton will move back into the second row alongside Alex Brown, which means Alasdair Strokosch, who started for Scotland against Ireland last Saturday, wears number six, Akapusi Qera comes in for Andy Hazell at openside and Luke Narraway wears the number eight shirt.
Hazell is ruled out with a slight neck injury which means Qera will make his 11th start of the season following his try against Newcastle off the bench last weekend.
"Balance is important and I think this is a side that has a lot of capability," Ryan said. "There is also a great deal of know-how and experience on the bench and at certain times they will also be crucial.
"We need to ensure our preparation is right and if we do that then we are capable of creating a threat against a lot of sides. Harlequins are a real threat and to pick off Saracens last Sunday was a very significant result for them - it will be a tough game."
On the bench, hooker Andy Titterrell will be joined by prop Alasdair Dickinson, lock Marco Bortolami and number eight Gareth Delve.
The three-quarter replacements are scrum-half Gareth Cooper, stand-off Chris Paterson and wing Mark Foster.
GLOUCESTER (v Harlequins, tomorrow, 2.45pm): Iain Balshaw; James Simpson-Daniel, Jack Adams, Anthony Allen, Lesley Vainikolo; Willie Walker, Rory Lawson; Nick Wood, Olivier Azam, Carlos Nieto, Peter Buxton (capt), Alex Brown, Alasdair Strokosch, Akapusi Qera, Luke Narraway. Reps: Andy Titterrell; Alasdair Dickinson, Marco Bortolami, Gareth Delve, Gareth Cooper, Chris Paterson, Mark Foster.
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