The flanker made just seven RaboDirect PRO12 appearances last term and as well as becoming a regular again he's desperate to improve on Edinburgh's 11th-place finish last campaign.
They've made changes in the coaching department, former Ulster and Northampton Saints director of rugby Alan Solomons has arrived at Murrayfield and is charged with aiding the club's revival.
And Rennie claims the early signs shown from the 63-year-old South African point to a potential improvement.
"We're under no illusions, this is going to be tough," said Rennie. "The thing is all the guys at the club are really looking forward to the challenge.
"Training's been going really well and we've seen improvements and hopefully we can show that when we start playing.
"From what we've learnt in the last two seasons, looking forward it's going to be a lot more positive.
"I think too many people were trying to do too many things and we didn't train well necessarily. Saying that this summer we've had a really tough pre-season which is slightly different.
"I'm just recovering from a shoulder op I had recently. I'm hopefully back in October and really looking forward to getting a good season under my belt.
"I'm getting there. I've got another month probably before I'm back into it properly but it's just one of these things. You do what the injury tells you and the physio team and the medical team. But I'm feeling stronger and getting fitter.
"You watch the other guys train while you're on the other side and you just want to get involved. I'm at that kind of stage right now but everything's going fairly positively."
Last season also proved fruitless in Europe for Edinburgh - they exited the Heineken Cup without picking up a win.
It made the semi-final charge the season before seem a million miles away for Rennie, who admits there is plenty of work to do to put things right.
"Obviously last season wasn't the best season and even the season before in the league it wasn't too good," added the Scotland international.
"We had a great Heineken Cup run (in 2011/12) but I think that maybe blinded us to some of the basic errors that we were getting wrong.
'We realised that for this summer and hopefully corrected them and we'll be working really hard on getting our basics and foundations - core, defence and fitness - right."