Both teams currently occupy a top-four spot but, with all four Welsh regions also still in the running, that could all change before the end of the regular season.
And while it is Ulster who are currently on target for a Ravenhill semi, a victory for Leinster could see the Dubliners or reigning champions the Ospreys jump into second spot at the end of Round 19.
For the home side it's a case of continuing where they left off as they strive for a glorious trophy-winning double following a stunning Heineken Cup win over English Champions Leicester last time out.
"You feel like the bit is between your teeth after a game like the Leicester one," said Leinster scrum-half Eoin Reddan.
"The buzz is high and you want to get back out there and follow on from that.
"In the squad there are a lot of guys who have been successful and to continue to be successful. Some people just have the bite to carry on. That's definitely within the squad and people will be aware of that and they will be looking to kick on again on Saturday.
"Everybody's pulling in the one direction and we're looking to get Leinster over the line in two competitions and that's not going to be easy, but it's certainly a massive ambition of ours.
"Saturday is a huge game. Derbies are always tight and I'm sure Saturday will be no different.
"I haven't won a Magners League yet and there are a few other players here who'd like to win their first Magners League title. It's a huge ambition for the squad."
Fellow Leinster star Kevin McLaughlin echoes his team-mate in admitting that Saturday's match up could play a huge role in deciding whether Leinster will be celebrating come the end of the season.
The Ireland back rower, who has just returned from a lengthy injury lay off, believes the tightness of the Magners League table makes this latest all-Irish affair a must-win encounter.
"It's still very congested up at the top. It's an important game in the context of the League," added McLaughlin.
"We have to take one match at a time and the fact that Ulster are ahead of us makes Saturday a must-win game.
"We're three points behind them at the moment and we see this as a key game. It's a key game for them as well so we're going to be in for a tough one this weekend.
"Ulster lost a ferocious battle against Northampton and they're going to be licking their wounds. The fact that they're only left in the Magners League may give them an edge but we're playing with a bit of confidence so I think it's going to be a tight game.
"Ulster have a strong set piece so that's going to be a key area. Obviously, we'll try and go after their setpiece, like we did against Leicester. But they're also strong at the contact zone so we'll look at that as well."
Leinster will be hoping for a repeat of December's win over Ulster
As for Ulster, the importance of Saturday's game isn't lost on the Belfast-based province either.
Their European dream may have ended for another season but hopes of a first Celtic crown since 2006 remain very much alive.
And while Sunday's 23-13 reverse to Northampton in Milton Keynes was undoubtedly a setback, six Magners League wins on the bounce will ensure the visitors will arrive in Dublin in decent spirits.
As South African back row Robbie Diack explains, this season will be something special if it ends with Grand Final glory on May 28.
"We are still in with a shout of reaching the Play-Offs and we will try to maintain the winning momentum that we had built up in the Magners League," said Diack.
"Reaching the play-offs is in our own hands and we know what we have to do. We've got to keep on improving and keep getting results.
"We still have a chance to achieve something special this season.
"We were very disappointed we lost against Northampton. Many people assumed they would give us a beating but our squad knew how good we are and believed we could cause an upset. We put up a good fight on the day but obviously it wasn't good enough.
"The Leinster game is crucial for us. They are incredibly tough opponents, especially at home. They will be full of confidence after beating Leicester but we have confidence in our own ability too."
Ulster have had plenty to celebrate in recent weeks
The size of the task ahead this weekend was perhaps best summarised by Ulster's operations director David Humphreys, who views Saturday's opponents as the benchmark for teams across the continent.
The 2008 Magners League winners and 2009 Heineken Cup Champions have been in superb form of late and former Ireland fly-half half Humphreys believes Leinster are currently the best in the business.
"I believe that Leinster are the most complete team in European rugby at the moment," said Humphreys.
"They showed on Saturday how good their pack is, going toe to toe with Leicester and coming out on top. Out wide they have players who can change a game with a moment of magic so we will have to be wary of that threat."
But while Humphreys and the whole of Ulster know they will have to be at their best at the RDS, former full back Bryn Cunningham is convinced they have what it takes to finish the season on an almighty high.
The 31-year-old, who retired through injury in October of last year, is expecting a positive reaction to their European exit this weekend.
"It's fantastic that there is another competition to look forward to and so much to play for," added Cunningham.
"The boys will regroup. They will be raring to go and will be up to the task for Leinster at the weekend.
"With three games to go I'm sure they can clinch a semi-final spot. The Magners League is there for the taking."
It will remain for the taking regardless of the result this Saturday but defeat in Dublin would undoubtedly make Ulster's challenge even more sizeable. And with both Ulster and Leinster facing similar scenarios, we're all set for what should be another magical Magners League encounter.
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