Simpson-Daniel, Gloucester's leading Heineken Cup try scorer, will sit on the bench after recovering from ankle ligament damage. He has not featured since Gloucester's 37-24 defeat at the Millennium Stadium against Cardiff in October.
There is also good news, provided both emerge from tomorrow's team-run unscathed, for both Mike Tindall and Olly Morgan, who picked up injuries in the defeat against Newcastle last weekend.
Tindall is scheduled to recover from a dead leg to skipper the side from the centre alongside Olly Barkley, while Morgan, who suffered an open dislocation to his finger, is also in-line to feature at full-back following tomorrow's final team-run, although Anthony Allen will remain on standby.
In the forwards, head coach Dean Ryan will make one change from the side that started last Sunday's 10-7 defeat at Kingston Park.
Hooker Olivier Azam returns to the starting line-up in place of Andy Titterrell and will form a front row alongside loose-head Alasdair Dickinson and tight-head Carlos Nieto.
Marco Bortolami will partner Alex Brown at lock, Alasdair Strokosch will continue at number six, Apo Satala will make his second Heineken Cup appearance at openside and Luke Narraway will continue at number eight.
In the backs, Gareth Cooper returns to the starting line-up following his return from a pelvic injury in Monday night's Guinness A League game and he will partner Ryan Lamb at half-back.
Should Tindall come through tomorrow's team-run, he will be joined by Barkley in midfield, while Matthew Watkins will complete a back three alongside Balshaw and Morgan.
"We understand that if we want to continue in Europe then this weekend is absolutely vital," said head coach Dean Ryan. "I think we are a pretty robust outfit and we need to take that into this weekend. We did some pretty smart things in attack against them [Cardiff] earlier in the season but they scored twice far too easily just before half-time - that is something you cannot afford at this level because it is so hard to go back and repair any damage.
"I am confident that if we are slightly more solid our attacking game will offer us opportunities we must try and exploit. "Heineken Cup weeks are quiet easy - there is no motivation required, there will be a lot of emotion and players respond to that. We are at home and we will be fighting for a result.
"There have obviously been some injuries this week and we have to try and work through that in a positive way."
On the bench, hooker Titterrell will be joined by prop Nick Wood, lock Will James and Adam Eustace.
Dave Lewis will be the scrum-half option, Willie Walker will cover stand-off and full-back, while Simpson-Daniel will complete the line-up.
Gloucester will keep Jack Adams, Anthony Allen and Mark Foster on standby until after tomorrow's final training session as cover for injuries.
15 Olly Morgan
14 Iain Balshaw
13 Mike Tindall (capt)
12 Olly Barkley
11 Matthew Watkins
10 Ryan Lamb
9 Gareth Cooper
1 Alasdair Dickinson
2 Olivier Azam
3 Carlos Nieto
4 Marco Bortolami
5 Alex Brown
6 Alasdair Strokosch
7 Apo Satala
8 Luke Narraway
16 Andy Titterrell
17 Nick Wood
18 Will James
19 Adam Eustace
20 Dave Lewis
21 Willie Walker
22 James Simpson-Daniel