Merrick led Victory to three grand final appearances, two grand final wins and two Premiers' Plates, with Muscat as his trusted on-field captain. The pair both left the club in 2011, with Merrick sacked and Muscat retiring, and the captain's armband was taken over by Leijer.
The defender, who made more than 170 appearances for Victory and is now plying his trade in South Korea, is close to both men and knows them intimately.
He believes the rivalry between them will only add to the spice of the occasion on Saturday.
"It's sort of the master versus the apprentice in a way," Leijer told The World Game.
"They had a lot of success together as player and coach. Now Musky's stepped to the other side.
"It's interesting how football works out and they've both ended up in this position. I suppose it adds to the fairytale, whichever way it goes."
Leijer was signed by Merrick as a 16-year-old to the Victorian Institute of Sport in 2002, before linking again with the coach at Victory in 2005.
"I've got a long history with Ernie, I credit most of my career to him," the Suwon FC centre-back said.
"He sort of spotted when I was 14 years old and nurtured me right through my Victorian Institute of Sport years and through my teenage years. Then obviously when he got the job at Melbourne Victory I was one of his first signings.
"I had a good education with Ernie, I learnt a lot about the game. Especially other stuff as well, he's very good at educating players and people about stuff off the field too.
"A lot of what I've done is because of Ernie and I'll be forever grateful for that."
Under Merrick the Newcastle Jets have impressively gone from wooden spooners last season to second place and a grand final spot this season, while the 65-year-old Scotsman has helped the Jets end an eight-year long finals drought and they are just one more result away from capturing the club's second A-League title.
"It's an amazing story and a credit to him what he's done there," Leijer said.
"One thing Ernie was very good at Victory was his recruitment. I suppose at the start of this year you could really see the squad that he was putting together at Newcastle was a good squad, it had proven winners like Daniel Georgivski and Roy O'Donovan. Good players from opposition teams like Petratos, Topor-Stanley, these are good, strong names.
"He got his recruitment right and a good start to the season builds belief and Ernie's very good at that side of the game. He tends to out-source as well and get people to help players with their belief, and that's something I particularly enjoyed when I worked under him.
"He's got this group of players to an amazing position and got a ticket for the big dance, an opportunity to lift the big trophy."
Muscat took the top job at Victory in 2013, replacing Ange Postecoglou, and Leijer spent two seasons playing under him before heading to Asia. The 44-year-old was under pressure at the turn of this year after a poor start.
But Muscat managed to turn the campaign around, with Victory finishing the regular season in fourth spot and then upsetting Sydney FC in extra-time in the elimination final.
Leijer believes that revival means whoever is victorious on Saturday would be fitting A-League champions.
"That's why whichever way the result goes this weekend, obviously I'm a Victory man and that's the side I will be barracking for," the 32-year-old said.
"But both sides have got great stories and the Newcastle turnaround from last year was phenomenal. Victory's form during the mid-part of the year, they lost key players like Mark Milligan and Jason Geria, so the Victory story is an amazing one in itself.
"Whichever way it goes it's been a remarkable turnaround for both clubs, it's fantastic they’re both there and in the hunt on the final day."