Victory saw the Ospreys move level on points with fourth-placed Glasgow prior to the Warriors' shock win at Munster on Saturday and a fine finish to the season could still bring the rewards they are after given that the teams above them in the table will all take points of each other in the run-in.
The Ospreys remain outsiders for the knockout stages as they still sit seven points adrift of Munster and 10 shy of second-placed Ulster but the fixture list is most definitely in their favour. While the four-times tournament winners take on Newport Gwent Dragons, Zebre and Connacht, Ulster face all three of the other teams in the top four, Munster have two away games prior to hosting Ulster and Glasgow's Scottish derby with Edinburgh would take on even greater significance if they lose to Ulster at Scotstoun next weekend.
"Winning keeps us alive. We said we wanted to ask questions of other sides and, by winning, we keep doing that," said Ress, after a Jeff Hassler try and 20 points from the boot of Dan Biggar saw off the reigning champions at the Liberty Stadium.
"We want to keep the season interesting. We're training well and there's excitement around the group. If we can get to the last game against Connacht with something to play for, we'll be thrilled.
"We've got to go three from three and there may need to be a couple of bonus points thrown in their as well. But that challenge does excite us.
"You do do the maths and look at if you get 15, team X has got to get X amount of points. If we get to a position where some of the sides have got to win two out of three, that's tricky considering the fixtures."
Rees admits the performance against Leinster wasn't perfect but he was delighted with the way the Ospreys battled to a vital victory after the Irish giants had set up a nervy finish.
Having led 19-10 with half an hour remaining, the Ospreys were pegged back to all square after 68 minutes before Biggar struck twice more from the tee.
"Leinster are a champion side. They asked so many different questions, as they always do. They'd come off a tough turnaround but top players like (Jamie) Heaslip and (Cian) Healy were banging at the door and we showed a lot of spirit, grit and resolve to hang in," added Rees.
"We didn't always have the control we desire, especially in the second half. There were a few setpieces that we slipped off and allowed them to build their score and put us under a bit of pressure. But we did rally, and in the last quarter we shut up shop and gained a penalty ourselves and put the game to bed.
"Some of our attacking play really challenged Leinster at times. I think we're showing progress there. There were strong performances from people who are growing in the shirt. Whether we make it this year or not, I'm confident we're going to be a good side in 12/18 months, and for the future of the Ospreys."
One man who really stood out in Swansea was No8 Dan Baker. The 21-year-old put in a man-of-the-match display against British & Irish Lions tourist Heaslip as he came of age with some stunning footwork and strong ball carrying against the very best.
"Dan's mesmeric," continued Rees. "We've seen him come through since he was 16 and we've known he's got that ability. He's starting to realise that potential.
"He can beat someone in a metre of space and, after a nervous start, he had a couple of little moments which excite us for the future.
"Watching him develop over the past 12 months into someone with an aptitude for the professional game, who understands the demands behind the scenes, means he can hit the ground running. We have him and a whole host of young forwards coming through, and line-breakers behind the scrum now, so we feel we're heading in a decent direction."