Horan's inclusion in the Munster matchday squad for the first time since mid-October, owing to surgery for a minor heart ailment, is the only change to the panel that secured a six-try win over Benetton Treviso last Saturday.
Back rower David Wallace fully recovered from the calf injury that saw him sit out the second half of that game.
And while Horan confined himself to a simple 'just delighted to be back in the squad' comment, his Munster colleague of 11 seasons, lock Donncha O'Callaghan, was a little more forthcoming.
"It's great, it really is great to have him back. We were all concerned when he had the knock but besides anything else it's just brilliant he's over the whole thing," he said.
"Marcus has been such a huge part of what this Munster squad is, and although someone has to lose out and that's a tough thing on them, it's a great boost to have him in for this game."
And commenting on the Pool 1 decider, O'Callaghan expects the same intensity of any of the big games Munster have played in before.
"This will be right up there with the toughest we've ever faced. They'll fancy their chances, in fact they make no bones but that they're coming here to win. That's the confidence they have.
"So what we have to do is just get every aspect of our game right for every minute of the eighty odd that'll be played. We're guaranteed nothing unless we win and that's our mindset."
The Corkman added: "Home advantage is great and it goes without saying how important our supporters are.They deliver in spades off the pitch but we have to do it between the touchlines.
"The incentive for us is not just getting to the next stage. It's getting there with a home advantage because we realise how important a home quarter-final is to the economy of this region and even more particularly so in these tough times."
MUNSTER (v Northampton Saints): Paul Warwick; Doug Howlett, Keith Earls, Jean de Villiers, Denis Hurley; Ronan O'Gara, Tomas O'Leary; Wian du Preez, Denis Fogarty, John Hayes, Donncha O'Callaghan, Paul O'Connell (capt), Alan Quinlan, Niall Ronan, David Wallace.
Replacements: Damien Varley, Marcus Horan, Tony Buckley, Donnacha Ryan, James Coughlan, Peter Stringer, Lifeimi Mafi, Ian Dowling.