Wielding a six-second gap on Mitchelton-Scott's two-time defending champion Daryl Impey at the start of the 149.1km Glenelg to Victor Harbour leg, Porte received the same time as stage winner Giacomo Nizzolo.

But despite the best efforts of the Tasmanian's Danish teammate Mads Pedersen, Porte's main general classification rival could not be stopped from winning eight sprint bonus seconds.

Willunga Hill - a stage Porte has won six years running - marks the final stretch of the TDU and even with Impey likely to win more bonuses, Hadspen's favourite son appears a good chance of adding to his 2017 title.

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"It's all to play for," 34-year-old Porte said.

"We expected Mitchelton-Scott were going to do that and Mads did a good job to take some seconds. It's not a massive deficit.

"Mitchelton were good today, and they exploded it in the final. It's going to be a hard race [on Saturday].

"That's it - I think if we can win the stage, we can win the race. I was a little bit isolated today, so hopefully [Saturday] the boys are on top."

The only rider to even win back-to-back TDUs, Impey hailed his teammates for "giving it everything" to help win him a three-peat.

"The whole week we've been trying to get into the lead here; it's achievable to beat Richie," the South African said.

"Two seconds is going to be really tight and close but we've given ourselves the best chance possible. The boys have worked incredibly hard all week and done an amazing job."

Porte (26 points) also sits second in the king of the mountain classification behind CCC rider Joseph Rosskopf (35 points).

Saturday's 151.5km TDU finale begins at 10.40am, with the first riders expected to cross the line about 2.30pm.

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