The veteran Wales fly-half misses the Championship play-offs final first leg at Castle Park due to a calf injury.
Some would argue that aids Doncaster’s chances of causing an upset, but Cooke told The Yorkshire Post: “Callum Sheedy is still a very good 10.
“I don’t know whether Gavin would play 12 or 10 if he was fit.
“They looked to have fallen out a little bit with Matthew Morgan since he’s leaving and they haven’t really missed Gavin while he’s been out.
“That said, when you’re quiet for 79 minutes and then make a half-break for (Tom) Varndell to score as he did up here, it shows how important he can be.”
That last-gasp score prevented Doncaster from completing a double over Bristol in March when they cruelly lost 31-29.
However, despite winning at Bristol and coming so close at Castle Park, few people believe Knights have a chance now, which has irked Cooke.
“Everyone outside the club seems to say Doncaster have done really well just to get to the final, which I think is a little condescending,” he said.
“I feel there is a bit of envy there from some.
“The guys here set some targets back in June or July and one was to make the top four.
“We got off to a good start and they have carried themselves with a lot of pride, integrity and desire to get to where we are now.
“Some people outside of here still think there’s been a bit of luck involved, but I can say there’s not been much of that.
“They have deserved everything they have got so far and they will take confidence from what they have already achieved.”
Doncaster have been able to name the same squad for the third game running, which is a major help ahead of such a definitive fixture.
Cooke added: “It’s a big part of why we’ve gone so well. We’ve had some real consistency with our selection apart from the early part of the season.
“Back then, we lost Simon Humberstone – our No 1 target for 10 – and then Declan Cusack stepped up and broke his cheekbone against Nottingham.
“But that gave some people five or six weeks’ rest, which has probably helped us now at the end of the season. Given we’ve such a small squad, to name the same squad three weeks on the bounce is great for us.”
Bristol, whose £3m plus salary bill dwarfs the estimated £750,000 of their fellow finalists, see Will Cliff, Jack Tovey and Marco Mama all return to the side that defeated Bedford Blues 45-19 in their semi-final second leg.
Captain David Lemi and Championship player of the year Jack Lam have recovered from minor knocks to feature.
Olly Robinson is back from a dead leg on the bench, but Jack Wallace, Mitch Eadie, Marc Jones and Henson are still absent and Martin Roberts, Gareth Maule and Nick Koster drop out.