Hooper will partner Dave Attwood in the second row, with Josh Ovens set to make his first Premiership start of the season on the blindside flank.
Former Army back Semesa Rokoduguni will also appear in the competition for the first time, partnering Matt Banahan in the centres, with Kyle Eastmond returning to the wing.
Michael Claassens and Stephen Donald will also return to renew their half-back partnership.
Harlequins have made seven changes to the starting line-up that beat Bath in the LV=Cup - with New Zealand international Nick Evans returning to action.
Evans, fit again after an ankle problem, will team up with scrum-half Karl Dickson.
Ugo Monye, George Robson and Jordan Turner-Hall are all free to start after being released by England, while Luke Wallace and Tom Guest join Nick Evans in the back-row.
On the bench, Jordan Burns is in line to make his first senior appearance for the club.
Bath: 15 Nick Abendanon, 14 Kyle Eastmond, 13 Semesa Rokoduguni, 12 Matt Banahan, 11 Tom Biggs, 10 Stephen Donald, 9 Michael Claassens, 1 Charlie Beech, 2 Lee Mears, 3 Anthony Perenise, 4 Stuart Hooper (c), 5 Dave Attwood, 6 Josh Ovens, 7 Guy Mercer, 8 Simon Taylor. Replacements:16 Brett Sharman, 17 Alan Cotter, 18 Kane Palma-Newport, 19 Dominic Day, 20 Ryan Caldwell, 21 Will Skuse, 22 Mark McMillan, 23 Jack Cuthbert.
Harlequins: 15 Tom Williams, 14 Ugo Monye, 13 Matt Hopper, 12 Jordan Turner-Hall, 11 Sam Smith, 10 Nick Evans, 9 Karl Dickson, 1 Mark Lambert, 2 Joe Gray, 3 Will Collier, 4 Olly Kohn, 5 George Robson, 6 Tom Guest, 7 Luke Wallace, 8 Nick Easter (c).
Replacements:16 Rob Buchanan, 17 Darryl Marfo, 18 Kyle Sinckler, 19 Pete Browne, 20 Joe Trayfoot, 21 Jordan Burns, 22 Rory Clegg, 23 Seb Stegmann.
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