They were left with a wafer-thin chance of reaching the Heineken Cup knock-out stages in the wake of Sunday's home defeat but Rennie believes Edinburgh's shortcomings made the English side look better than they are, and that they can secure victory at Kingsholm this weekend.
The fit-again Scotland flanker said: "It was our turnovers that killed us at Murrayfield, rather than Gloucester. We didn't manage their elusive back three nearly well enough. We left too many gaps for them to run into and the result was chaos. You will never beat a team like them if you don't look after the ball properly.
"I really do think we can turn it round at their place because, when you look at things closely, we were still in the game at Murrayfield in spite of all the mistakes. We don't often play the big English Premiership clubs. They have a different approach to the Pro12 teams and they are really good at the attritional stuff - messing the ball up for the opposition. But the bottom line is we need to keep the ball; when we did get it right, we carved them up."
Rennie is thrilled to be back playing but knows he will have to step up the standard to have any hope of a Scotland comeback in the Six Nations.
"I didn't feel I got into the game at all - it was frustrating - but it is great to be back at this level," he said. "The big thing for me is I still care. When you come back, you're not sure how you are going to feel."