The powerful attack-minded right-back has scored two goals in his first two starts for Town and is likely to feature from the off at Ipswich today.
But the Australian, 24, who is initially on loan from Newcastle Jets in his homeland until January, admits he needs to brush up on his defensive duties.
“Coming over, when I’d spoke to Sam, he’d watched a couple of games and he said I can really contribute going forward,” Millar said.
“There’s things in my game I need to work on – defensively is somewhere I can definitely add.
“Working with Sam, body positions, shape, one-on-one defending, is all something I can definitely improve.”
Millar, remarkably, was top scorer from right-back for his parent club before switching to England.
He added: “The running joke was (saying) that I played right wing when I played right-back.
“We had a turnover of strikers leaving so that helped me get up there in the goalscoring.
“One thing I do like to do is get forward and contribute that way. I think that’s reflective of the modern-day full-back – you’ve got to be up and down, helping out going forward and going back.”
Millar has made clear his ambition to join Shrewsbury permanently after his loan ends in January and is confident Town can climb clear of the League One drop zone.
“I think we’re very optimistic,” he said. “I know results aren’t what they should be, but we’re very optimistic.
“Looking at the last couple of performances, results aren’t there, but we were all over Swindon. We just need to see out games.
“The good thing is if you string three or four wins together then suddenly you’re top 10 or looking mid-table.”