Yet the impressive forward says captaining Leeds Rhinos in their battle at the wrong end of Super League is his biggest yet.
Merrin, who took on the job when England centre Kallum Watkins left for Gold Coast Titans at the end of June, leads the side into yet another crucial contest as they visit bottom-placed London Broncos on Sunday.
The West Yorkshire side, who sit eighth but still just two points clear of last spot, are one of five clubs still fearing relegation with only three games remaining.
As fascinating as it is for the neutrals to observe, for those in the midst of it all, the tension is ratcheting up with so much on the line.
Despite all his experience and measured approach, it is no different for Merrin, either.
The 29-year-old arrived this season as one of Leeds’ first-ever ‘marquee’ players, an NRL Grand Final winner who envisaged winning trophies at Rhinos rather than battling the drop. Still, he has felt the pressure and levels of expectancy, although anyone who has seen his all-action, commanding displays would argue otherwise.
On the captaincy, Merrin conceded: “I didn’t expect it.
“I was overwhelmed to take it on (considering) the heritage and passion of the club, and to be able to lead the team and the culture here. It’s something I’m humbled about and very privileged to be able to do.
“It’s been a great challenge, especially the way we’re going, too, but I’m enjoying it.
“I’ve never been as challenged as much as I have been now and it’s definitely a growing period for me personally.”
Asked why, Merrin responded: “That’s the biggest thing – we don’t have relegation back home.
“Obviously you have your tough seasons back home but you’re always promised a job the next year.
“But over here you’re not just playing for yourself but other people’s jobs and for the club, too, to keep the club going. To have that on your shoulders is not the easiest sort of thing to manage.
“But it has been a great challenge to get to see and test your true character when you go through things like this.”
Appreciative Leeds fans are certainly glad to have Merrin on board, the robust loose-forward whose 57 offloads are more than anyone else in Super League and whose constant drive has been so central to seeing Rhinos rise up the table. Indeed, they seemed to have reached safety when they backed up a stunning 44-0 win at Huddersfield Giants with a similarly impressive 48-8 success over Catalans Dragons.
However, they then threw away a promising position to lose at home to leaders St Helens before the Wembley break.
When London then headed to Perpignan and stunned Catalans, suddenly the bottom-placed Broncos were level with both Hull KR and Huddersfield and just two points adrift of Wakefield Trinity and Leeds.
“The footy gods are putting on a clinic for us, setting it all up for a good finish,” admitted Merrin, as he considered Super League’s dramatic final run-in, Leeds at London and then home fixtures with top-five chasing Salford Red Devils and Challenge Cup winners Warrington Wolves.
“It’s definitely going to be a big challenge for us but I’m confident in our team and what we’re capable of doing.
“We just need to focus on us. The two weeks before St Helens we’d put on some great performances so we know what we are capable of if we just focus on us. So, that’s what we’ve been doing this week preparing for a big game.”
Promoted London refuse to go away having already beaten Rhinos at Headingley – before Dave Furner was replaced by Richard Agar – and twice defeated St Helens, Catalans and Wakefield Trinity as well as overcoming champions Wigan Warriors.
Merrin admitted: “It’s all credit to them. They play for the full 80 minutes, are full of energy and work hard for each other.
“It’s definitely going to be a big game for us, especially playing at their home ground and the way the table is looking.
“But we just need to back ourselves and play consistent footy with the ball.”
Prop Ava Seumanufagai has passed a head test and will be available after suffering concussion two weeks ago. Veteran forward Jamie Jones-Buchanan could make his first appearance since May but long-term casualty Stevie Ward will not be risked.