Cornes, 26, was at his negating best last week, holding Hawthorn skipper Sam Mitchell to just 16 possessions and playing a big part in the Power's 30-point win.
Dal Santo has brushed aside an inconsistent 2008 season, which saw him dropped back to the VFL for one match.
The former All-Australian has averaged 31 possessions and a goal in the opening four games and been instrumental in St Kilda’s perfect start to the year.
Cornes said Dal Santo was in Brownlow Medal-winning form.
“St Kilda has a terrific midfield and I think Dal Santo and Leigh Montagna have been two of the best players in the comp so far,” Cornes said on Monday.
“The best thing about him (Dal Santo) is his skill. We certainly don’t want him kicking the ball inside50m that often because he’ll cut you up.
“It’ll depend on how we set up (as to whether we tag him or not), but at this stage I wouldn’t think we’d be giving him too much room.”
Port Adelaide was relentless in applying pressure to the Hawks and even out-muscled the reigning premier at stoppages.
Cornes said his side would need to bring the same physicality and intensity to the game to conquer with the undefeated Saints.
“St Kilda has always been a great tackling side. I think Lenny Hayes led the comp in tackles for five or six years-in-a-row and Luke Ball as well,” he said.
“They’ve got some really hard nuts in their midfield. Clinton Jones has really stepped up.
"He does some run-with roles and gets lots of tackles as well. They’re a tough side and there’s no better challenge to play against the tough sides.
"We’ve matched it with everyone in that area so far this year.”
Saturday’s upset win at the MCG has seen Port Adelaide move into fourth spot on the AFL ladder, one game clear of fifth-placed Carlton.
Coach Mark Williams said Saturday's win was the club’s best-ever regular season victory and Cornes said Friday night’s game could prove just as important in the long-term.
“We’ve identified these three weeks, including the Hawthorn game, as a huge three weeks for us against Hawthorn, St Kilda and then Adelaide,” Cornes said.
“The next three weeks could really set our season up and St Kilda is the form side in the competition at the moment along with Geelong. We’ll definitely see where we’re at and get a better indication after this week.”
