Impey will be joined in the Mitchelton-Scott line-up by newly-crowned Australian time trial champion Luke Durbridge and road race bronze medallist Cameron Meyer.
Mathew Hayman, the 2016 Paris-Roubaix winner, is also on the roster for what will be his final race as a professional rider before he takes up a non-riding role with Mitchelton-Scott. The seven-man roster is completed by Alex Edmondson, Lucas Hamilton and Michael Hepburn.
"Going back to any race as defending champion always puts a big target on your back," Mitchelton-Scott directeur sportif Matt White said in a statement from the team. "Daryl is leading our team and we have won the race four times already, so all teams are looking at what we do.
"We are ready for the challenge and we have brought a solid team to aid Daryl in his attempt to defend his title, something that has never been done in Tour Down Under history."
In recent years, Mitchelton-Scott have balanced their GC challenge with the sprint ambitions of Caleb Ewan, but there is no designated sprinter in the squad this time around. Ewan will make his WorldTour debut for his new team Lotto Soudal at the race.
"Without Caleb or a sprinter, it certainly decreases our work load throughout the week," White said. "This is a big advantage for us because we are able to focus our energy expenditure. In the past we were basically trying to win every stage, which was a massive load and stress for the team."
Twelve months ago, Impey helped Ewan to win stage 2 and then moved into the overall lead after he placed second behind Richie Porte on the pivotal penultimate stage to Willunga Hill. The South African believes his condition is roughly similar this time out and agreed that the absence of a dedicated sprinter in the Mitchelton-Scott team could benefit his overall challenge.
"I will take it day by day, see where I am at and see where everyone else is at too," Impey said. "The biggest change for me, and for the team, is that without Caleb we don't have to worry about his lead-out, so I can put more energy into my own goals."
Another difference on the 2019 Tour Down Under comes in the route, which has been billed as the most difficult in its 21-year history. The traditional hilltop finish at Willunga now takes place on the final stage rather than the penultimate, though Impey does believe it will alter the tenor of the race.
"I like the new route. I don't think Willunga on the last day will change much," Impey said. "It makes it more exciting, but for me, like last year, I just need to take time where I can and then hope it's enough."
Richie Porte (Trek-Segafredo) has won atop Willunga Hill in each of the past five editions of the Tour Down Under, though he has won the overall classification just once, in 2017. White believes that switching the climb of Willunga to the final day increases the climb's significance.
"This race has traditionally been won by very small margins, and certain types of riders always had the ability to go after bonus seconds on the final circuit race in Adelaide," White said. "With that gone it places even more importance on the last kilometre of Willunga. This year's edition is the toughest edition in its history with three key climbing stages, something we have never had before."
The Tour Down Under gets underway on Tuesday, January 15. The People's Choice Classic, the curtain-raising criterium, takes place on January 13.
Mitchelton-Scott team for Tour Down Under: Luke Durbridge, Alex Edmondson, Lucas Hamilton, Mathew Hayman, Michael Hepburn, Daryl Impey, Cameron Meyer.