Full-back Merrett and his fellow key defenders Matt Maguire and Joel Patfull have been pitted against a host of young Lions forwards trying to impress coach Michael Voss.
Aside from captain Jonathan Brown, the race for key forward posts is well and truly on.
But there's no way Merrett, Maguire and Patfull are giving ground easily - even at training.
Merrett said whether it was Jordan Lisle, Aaron Cornelius, Melbourne recruit Stefan Martin or rookies Marco Paparone and Michael Close, the defenders were not giving an inch.
"At times it can get narky and aggressive but that's exactly what you want because you want to drive high standards," Merrett said.
"It's only going to make us better. Where our group's at, we're developing and breeding that into the young guys to be aggressive, it's perfect.
"We're all over the forwards at the moment."
In 2012 Merrett spent most of the season alongside Brown in the forward half as Voss struggled to find a younger sidekick who could consistently produce.
The 28-year-old more than held his own in the forward/ruck role, kicking 26 goals in his 17 starts forward.
Now back in his more familiar surroundings of the defensive 50m, Merrett was in the perfect position to assess which forward was travelling the best.
Voss has even had Irishman Niall McKeever training up front as he searches for answers ahead of the season.
But Merrett went for a second-year Lion when asked who he thought had had the best pre-season.
"Probably Jordy Lisle at this stage," he said.
"He's really stepped up, definitely matured, talking a lot more and he's improved his fitness. From my point of view, at this stage he's up there.
"Also Stef Martin. We've got him across for that reason, to try and fill that void, so we'll be looking for Stef to step up.
It's all about options, that's where the game's headed. So plenty of competition and plenty of options. That spot will be up for grabs all year I reckon."
Michael Whiting covers Brisbane Lions news for AFL.com.au. Follow him on Twitter: @AFL_mikewhiting
