Back rower Mowen knows all about Lealiifano's talents having played with him for two seasons in Canberra and he is predicting big things for the 25-year-old this evening.
It doesn't come much more dramatic than making your Test bow against Britain and Ireland's elite in front of a packed out Suncorp Stadium but Mowen believes Lealiifano has the perfect temperament to shine of the biggest stage of all.
"This game will suit Christian perfectly. He's a massive pressure player. He's done it time and time again for the Brumbies," said Mowen, who has been delighted to see his club colleague bounce back from a horrific ankle injury when he was on the verge of a Wallaby cap last season.
"If there's a pressure shot to be taken, he's the guy you want taking it because he always puts it through. I don't think he's ever missed a pressure shot, and I think that says a lot about him as a bloke.
"He's a guy who wants to be challenged in those hard environments and obviously Saturday night's going to be exactly that. I know from playing a lot of footy with him - as does Adam Ashley-Cooper, who'll pair up with him (in midfield) - that he's the guy you want in those situations.
"He's a great attacker and a great defender. People were probably questioning whether he could go on with his form from last year after he was halted by a big injury but he's shown this year that he's gone to the next level. I think that says loads about his character."
Mowen's character can't be questioned either after he finally forced his way into his country's matchday squad after repeatedly being overlooked in the past.
The 28-year-old, who usually plays at No8 rather than the blindside flank, has endured a rocky road to the top, winning just one cap for his hometown franchise the Reds before being unceremoniously released by the Waratahs in 2011.
He bounced back in brilliant fashion, leading the Brumbies to within a single win of the Super Rugby play-offs last season and to the Australian Conference title in 2013 and is now all set to embrace the opportunity that his supporters feel should have come his way earlier on in his topsy-turvy career.
"It's funny how it all figures out but I feel extremely fortunate to be here. To be making my debut in my home town, in front of my family and friends, is a massive reward," added Mowen.
"For me throughout my career, year on year, I've just chased improvement. This is always where I wanted to be. There are certain times when you question whether you'll get there or not, but I'm very fortunate that I've got a very good support network around me who pushed me to stay in Australia and keep pursuing this. It's not only a huge reward for me to achieve this goal, it's also a massive reward for them for all the faith they've shown in me over the years."
So what does Mowen expect when he runs out for his first international appearance against Warren Gatland's troops tonight? In short, a huge battle up front but one that he knows could ultimately bring big rewards for the Qantas Wallabies backline if the pack can get on top in the tight.
"From seeing the Lions' previous games, the forward pack that they've picked is definitely the guys who are in the best form. There's really good leadership throughout their pack as well.
"You know what they are going to bring: they're going to bring a strong set piece, they're going to be good at the scrum, good at the lineout, good at the maul, good at the pick and drive, so if we're not doing our jobs up front from one to eight then we're not going to give our guys opportunities.
"We certainly feel that we've got really good firepower in the backs and all we've got to do is make sure we give those guys opportunities. It will be up to us to put a good foundation down for those guys to attack."