The Red Bull Ampol Racing team principal and co-driver labelled himself “rusty” on a day where he wound up sixth in the co-driver practice session.
The #88 driver trailed the sister #87 Chevrolet Camaro of Scott Pye by just over one tenth of a second at the end of the 30-minute session.
“I just didn’t get it together today, couldn’t get much of a rhythm all day,” said Whincup.
“I’ve got some work to do overnight. Broc’s giving me the end-of-day rides which gives me a few more laps to try to find a bit of a rhythm, but I’m a rusty sheriff’s badge at the moment.
“It’s probably going to rain tomorrow, so it’ll be nice to run around on the new wet tyres. So, if it does rain, it’d be great to get some laps on that.
“I just need to go out and find a rhythm tomorrow.”
Broc Feeney, who sits third in the drivers’ championship behind Will Brown and Chaz Mostert, said he will give Whincup extra running on Saturday. Two practice sessions remain before qualifying.
“JDub got some laps in today, so we’ll try and get some more for him tomorrow and, see what the weather brings,” said Feeney.
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Feeney and Whincup were only 17th fastest in Practice 1 but improved to fifth in Practice 3.
“We stuck to our plan today, which was good because it didn’t look pretty at the start of the day,” said Feeney.
“I think overall, it’s ended well. We were probably missing a little bit for the first two sessions, but I think how we structured our practices meant that was going to be the case.
“I only got one run this morning, but felt super comfortable this afternoon, so really happy with where we’re at.
“I just struggled a bit on that green run there at the end. We’ve got a bit of work to do with our green tyre running, but apart from that I’m really happy.”
Practice 4 is scheduled for 9:55am AEST on Saturday, which will be followed by Practice 5 at 12:05pm.
Qualifying is set to begin at 2:15pm before the Top 10 Shootout at 5:25pm.