There is also an entirely new front row, a change at lock and a rotation in the centre.
Alongside Boer in the back row, Adam Balding comes in for his first senior start of the season at number six, while Luke Narraway replaces James Forrester in the number eight position - both played in the Guinness A League on Monday.
"We have always said that we are capable of making eight or 10 changes and still be very competitive," head coach Dean Ryan told www.gloucesterrugby.co.uk
"There is tremendous depth in our squad and this is very important for our players because we need to provide them with opportunities and support them all the way.
"We will try some different combinations but this is not a secondary competition - we want to win every game we play in but it is an opportunity to try some other guys."
In the front row, Mefin Davies returns at hooker and will be partnered by youngster Jack Forster on the tight-head and Patrice Collazo at loose-head.
Adam Eustace retains his place in the second row and will be partnered by Will James. The backline is less disrupted and contains only one change - Jack Adams, who has scored two Premiership tries this season against Bath and Northampton, gets a run in place of Anthony Allen.
The rest of the three-quarters are intact with Rory Lawson partnering Ludovic Mercier at half-back, Olly Morgan at full-back and Mark Foster and James Bailey on the wings.
The bench is also packed with experience. Olivier Azam and Nick Wood are the front row options, while Italian skipper Marco Bortolami is included before he jets off for Italy's two World Cup qualifiers.
Flanker James Merriman, England scrum-half Peter Richards, utility back Rob Thirlby and Brad Davies complete the bench.
GLOUCESTER v Ospreys (tomorrow, 7.10pm): Olly Morgan; Mark Foster, Jack Adams, Rudi Keil, James Bailey; Ludovic Mercier, Rory Lawson; Patrice Collazo, Mefin Davies, Jack Forster, Will James, Adam Eustace, Adam Balding, Jake Boer (capt), Luke Narraway. Reps: Olivier Azam, Nick Wood, Marco Bortolami, James Merriman, Peter Richards, Brad Davies, Rob Thirlby.
THE match tomorrow will be shown live in the Shed Bar at Kingsholm - the doors will open at 6pm for the 7.10pm kick-off.