Hey, brother

While he deemed the WD-40 Phillip Island SuperSprint a positive weekend, it's unlikely Paul Dumbrell will be back in the main game at the season finale.

The 2012 Bathurst winner is fighting young gun Cameron Waters for the Dunlop Series title and has full focus on applying the pressure and pegging back the young gun's 149-point lead across the two races at the Coates Hire Sydney 500.

Dumbrell stepped into his brother Lucas Dumbrell's team to fill in for a sick Nick Percat at the last second on Saturday and while he enjoyed the experience, he was expecting it to be a one-off.

"All I've thought about is the Dunlop Series - I haven't thought about anything else other than that," Dumbrell told v8supercars.com.au when asked about the Coates Hire Sydney 500.

"Sydney is a really tough race and you'd be hard pressed to do both.

"You see Cam stepping out of the Pepsi car for that weekend as well, so it'd be very much unlikely I'd do anything else."

Funnily enough his Dunlop Series adversary Waters has been standing in for an injured Chaz Mostert since Bathurst, but the Pepsi Max Crew's other co-driver Steve Owen will contest Sydney to leave Waters to focus on Dunlop Series.

LDM is already believed to be hunting a back-up option within the Holden stable while waiting for more information on Percat's condition.

The 2011 Bathurst winning driver suffers from an infection after sustaining a burned foot at the Gold Coast 600. While he had planned to contest the weekend, the infection flared up before practice on Saturday, leaving Dumbrell to fill in at the last minute.

It was so last minute, he jumped straight in the car with mismatched gear for practice three and had to pit to sign the required forms to race.

V8 Supercars Permanent Medical Delegate Dr Carl Le visited Percat last night in hospital and was hopeful he would be ready to get back behind the wheel in Sydney.

"He's much better and in good spirits," Le said.

"He is being looked after by a Professor of Infectious Diseases, Joseph Toressi.

"Hopefully Nick will only need a few days in hospital and then home again. He should be much better for the Sydney grand finale."

The late substitution for #222 was one of four driver swaps for the weekend, with Chris Pither taking the wheel at Super Black Racing and Dean Canto at Erebus.

Those changes were to find performance gains for 2016 - and with Dumbrell, his recent experience in Triple Eight cars was valuable for the team.

He explained the LDM Commodore was not the same spec car he drove with Jamie Whincup during the enduros, but they had made progress all the same.

For 'PD' Phillip Island was the track he though was toughest to tackle with a late call-up, given how demanding it is on drivers.

"We made in-roads on the car on the weekend, but to be perfectly frank, I probably had more to give to the car than what the car had to give to me," Dumbrell said.

"A few more miles on Friday would've been ideal -but that's just how it goes.

"So we did our best, we got caught up at the end of the race at the back end of the 20 which is never ideal, but I think we made some progress for the weekend and the team's got some direction moving forward."

He found it "interesting" racing for his younger brother's team for the first time and commended the job team manager Barry Hay has done since joining for the 2015 season.

"It's good to see the massive improvements they've made this year," Dumbrell said.

"I've spent a little bit of time with the guys - just ducked my head in over the last couple of years - but the professionalism and preparation that Barry and the whole team, with Lucas, have done over the last six to 12 months has been great."

Dumbrell finished 21st in all three races across the weekend, in a similar position to the other substitute drivers and his teammate Tim Blanchard.