Iain Balshaw moves to full-back, Jack Adams comes in at outside centre and will partner Mike Tindall and James Bailey returns in place of James Simpson-Daniel, who picked up a rib injury.
There is also no James Forrester, who is still struggling with a sore knee, which means Adam Balding, who impressed in France last weekend, retains his number eight shirt.
"In a game of last week's intensity there are obviously some casualties and we are not in a position to risk anyone at this stage," Ryan told www.gloucesterrugby.co.uk.
"We have been involved in some extremely physical contests at the top end of Europe and the Guinness Premiership since the turn of the year and these things happen.
"Nevertheless, we have a strong squad for what is an important game for us - Leinster have obviously already won the pool but we want to test ourselves against that calibre of opposition."
There are also two changes at half-back where last Friday's second try-scorer Peter Richards resumes his regular position of scrum-half and Willie Walker comes in for Ryan Lamb at stand-off.
The forwards have a far more settled look - the only change coming in the front row where Nick Wood comes in for Christian Califano at loose-head prop.
He will be partnered by hooker Mefin Davies and tight-head prop Carlos Nieto. Marco Bortolami and Alex Brown are the locks, while Peter Buxton, Andy Hazell and Balding are the back row.
On the bench, there is a return for centre Rudi Keil following a shoulder injury.
"Europe has been a lost opportunity for us this season but there is still plenty on this game tomorrow and that is important to us," Ryan said.
"It's not dead, there will be a capacity Kingsholm crowd and we are fully motivated."
GLOUCESTER (v Leinster, tomorrow 7.30pm): Iain Balshaw; James Bailey, Jack Adams, Mike Tindall, Mark Foster; Willie Walker, Peter Richards; Nick Wood, Mefin Davies, Carlos Nieto, Marco Bortolami (capt), Alex Brown, Peter Buxton, Andy Hazell, Adam Balding. Reps: Olivier Azam, Christian Califano, Will James, Jake Boer, Rory Lawson, Ryan Lamb, Rudi Keil.