Aidan O'Mahony can remember facing Stephen O'Brien in Kerry training and the Kenmare forward being a nightmare to mark, starting out on the opposite side of the pitch and then suddenly appearing on his.
Over the years, the broad strokes of O'Brien's game have not changed - he's still the same tireless, pacy, direct runner - but there are now little nuances which make him more effective.
"A couple of years ago, he had his head down and he’d be running into cul-de-sacs," says O'Mahony, a five-time All-Ireland winner.
"I always used to do this thing where he’d get the ball and you’d be right beside him so that he’d put his head down and keep his head down so he couldn’t see the open space in front of you.
"He’s a nightmare for a defender because he’d go at you time and time again."
O'Brien first came onto the Kerry panel in 2013 during Eamonn Fitzmaurice's first year as manager.
"I knew him from the under-21s," Fitzmaurice told the Irish Examiner's football podcast following the All-Ireland semi-final, "I knew there was a serious player in there but I told him, 'Look, you're probably not going to make the panel this summer (2013) unless you absolutely shoot the lights out. But learn, soak everything up, develop yourself because come next year's league, you are going to be in our plans'.
"He ended up starting an All-Ireland final at the end of 2014 and winning an All-Ireland medal.
"Stephen is a great guy and his attitude and personality are exactly where you need it to be. He keeps looking to improve the whole time."
That desire to consistently improve is the catalyst which has turned the 28-year-old from possible starter to a player for whom the opposition must have a plan.
"He’s always been a powerhouse," says former Kerry teammate Darran O'Sullivan, "but he’s just brought a bit more finesse to his game. There’s nothing Stephen can’t do at the moment.
He’s a lot more aware. He’s coming from a lot deeper now. Sometimes you’d be trying to stay high up the field and it’s hard to see anything.
Now he’s going a small bit deeper and he’s able to see a bit clearer. And he’s able to duck in behind fellas. Like that, it comes with experience. The last couple of years, he’s obviously learned an awful lot. He’s just built on that.
I’ve good time for Stephen anyway, obviously, I played with him for a couple of years, and he’s a genuine, nice guy. There’s no bullshit or anything about him.
They could ask him now in the final, ‘Stephen we want you to play wing back’. Grand. He’ll do it. Then if an opportunity came late on and they said ‘Stephen you’re dead on your feet but we need you to make one lung[-buster]’ he’d be like ‘right grand’. He’d do it. He’s just a genuine guy.
I think it’s a confidence thing as well. He just looked so confident out there, he’s full sure of what he’s doing.
Already this championship, O'Brien has hit 1-11 - he has been on the scoresheet in every game bar the Munster semi-final against Clare. It is his most prolific summer yet for Kerry.
"His finishing has improved," says O'Mahony.
"That was one thing that might have let him down a little bit but if you’re going that pace, you’re finishing mightn’t be as accurate.
"I think he gets himself in better positions now and he takes the ball more into the scoring zones or that D there where it’s not percentage shots - he’s making himself very accurate."
"There was a time there when teams used to cheat off Stevo," says O'Sullivan.
"You’re not going to cheat off Stevo anymore."
Photo by Ramsey Cardy/Sportsfile
