It will be Glasgow’s fifth consecutive appearance in the play-offs and the game at the Sportsground will be shown live on Sky Sports 1 and BBC Two Scotland (ko 6.30pm).
Gregor has made a number of changes to the team that lost out 14-7 in Galway two weeks ago.
Glasgow's latest century man Peter Horne partners Mark Bennett in the centre with Alex Dunbar dropping out through injury.
Lee Jones is replaced by Sean Lamont on the left wing.
Finn Russell is at fly-half and forms a half-back partnership with Henry Pyrgos, who returns from injury and replaces Ali Price at scrum-half.
In the pack Gordon Reid and Fraser Brown continue at loose-head and hooker respectively, with Zander Fagerson replacing the suspended Sila Puafisi at tight-head.
In the back-row Ryan Wilson moves from openside to blindside flanker in place of Rob Harley, with Simone Favaro coming into the starting XV in the Number 7 shirt and Josh Strauss continuing at Number 8.
On the bench Ryan Grant returns from injury following a three-month spell on the sidelines, while D’arcy Rae, Adam Ashe, Duncan Weir and Taqele Naiyaravoro are also named in the matchday 23 this weekend.
Glasgow Warriors head coach Gregor Townsend said: “The players have worked really hard to secure a fifth consecutive play-off and we’re excited about the opportunity this represents.
Connacht are a tough opponent and have been playing well, but we’re fully focussed on what is required tomorrow night.
“We’re expecting a large number of Glasgow supporters in Galway and we know that they will create a lot of noise and really get behind the team.
“We’ve learnt a lot from the game a fortnight ago and we're determined to put in a performance of which we can all be proud.”
15 Stuart Hogg
14 Tommy Seymour
13 Mark Bennett
12 Peter Horne
11 Sean Lamont
10 Finn Russell
9 Henry Pyrgos
1 Gordon Reid
2 Fraser Brown
3 Zander Fagerson
4 Leone Nakarawa
5 Jonny Gray (Captain)
6 Ryan Wilson
7 Simone Favaro
8 Josh Strauss
Substitutes
16 Pat MacArthur
17 Ryan Grant
18 D'arcy Rae
19 Tim Swinson
20 Adam Ashe
21 Grayson Hart
22 Duncan Weir
23 Taqele Naiyaravoro
Not available due to injury: Alex Allan (concussion), Kevin Bryce (knee), Junior Bulumakau (foot), Rory Clegg (ankle), Alex Dunbar (knee), Jarrod Firth (concussion), Tyrone Holmes (foot), Sam Johnson (hamstring), Fergus Scott (shoulder) and Richie Vernon (shoulder).