"I've been ticking all the boxes (during the three months on the sidelines) ... I'm very confident in the hammy."
Rioli returned in the VFL grand final last Sunday, with both Clarkson and he confident of an improved showing at the MCG.
"I'm just there to cause chaos and and create some forward pressure," he said. "If I bring that tomorrow, I'm sure I'll get through the game."
Hawks skipper Luke Hodge agreed Rioli's defensive pressure would be his biggest asset.
"Everyone knows that Cyril doesn't need to get 20 possessions to impact on a game," Hodge said.
"When we're training ... and you have got the ball in your defensive half and Cyril is in the area, you panic.
"We know the exact same thing is going to be going through the Sydney defensive blokes' [mind] when they have got the ball."
Clarkson admitted his club "were running it a little bit fine in terms of time" with Rioli's recovery, but had no doubt it was the right decision to pick the 25-year-old.
"There's a level of risk in every player that runs out there tomorrow," Clarkson said yesterday. "It's a tough, brutal game.
"But the Swannies have got some risk too. [Nick] Malceski has got some risk, [Heath] Grundy has got some risk, [Sam] Reid has got some risk.
"The reality of big games, big finals, you try to pick the best squad you can possibly pick and we think Cyril is right to go."
Rioli was "very grateful" to have the backing of Clarkson.
A reserved character off the field, he knows the intense interest of finals well after playing in the 2008, 2012 and 2013 season deciders.
But this September has been a little different to most, with Rioli's much-analysed hamstring being one of the talking points of the finals series.
"I've been trying to dodge the TV cameras," Rioli laughed.
"That's all part of the game ... I've just been sticking to my rehab.
"But it has been a weird feeling - I haven't been playing football and that's always hard."
Rioli said he'd be happy to start or play as the Hawks' substitute.
Sydney coach John Longmire noted he had prepared for Rioli's selection, adding that the Swans hadn't "put any extra time into Cyril, we put time into all of them".
- AAP
