Someone wandering off the street to watch the Chiefs go through their main team training run before tomorrow night's Super Rugby match against the Highlanders would have been confused.

There was a backline without Aaron Cruden and Sonny Bill Williams, while reserves Andrew Horrell and Lelia Masaga also cried off the bulk of the run.

No8 Kane Thompson was another mid-run defection with a niggling injury.

All had been named in the team just unveiled by the Chiefs at the start of the training session yesterday, with five changes from that which started the last match against the Blues four weeks ago.

But afterwards Chiefs coach Dave Rennie was upbeat about his players' chances of fronting at Dunedin's Forsyth Barr Stadium, even though an extra back will be taken south today as a precaution. Though Cruden was selected at first five-eighth for his 17th start in 17 games, the Achilles tendon problem he suffered in last Saturday's All Blacks test at Waikato Stadium has meant he has not trained at all this week.

"We're going to run him tomorrow in the captain's run," said Rennie.

"He's improved heaps and we're pretty optimistic, so if the progression keeps the same way it has been, then he'll be right to have a bit of a jog-through tomorrow and play on Friday."

Horrell is earmarked to take Cruden's place at No10 if Cruden cannot start but Horrell rolled his ankle in a gym session on Tuesday and was unable to train yesterday. Fullback Robbie Robinson filled in the pivot spot for the training session.

"But he should be back into things tomorrow, and Lelia looks pretty good with his knee coming right and should be right to take his place on the bench tomorrow – but all these things we'll sort out tomorrow."

Masaga's knee – the same one injured in the first game of the season – locked up on him after the Rotorua practice game last week and he got it iced midway through yesterday's session as a precaution.

Williams was given yesterday off by the coaches after a heavy workload with the Chiefs and All Blacks.

"He's been in the last two days but we just wanted to freshen him up because he's played a lot of footy, so we decided to give him a day away," Rennie said. "He'll come back in for the captain's run tomorrow and he's pretty clear on what we're trying to do in this game and we just need to make sure his body's in good nick and his head's clear."

Tim Nanai-Williams gets his first start for some time since injuring his groin and he may have to move to fullback if Cruden is ruled out, but otherwise his replacement of Maritino Nemani is the only change to the backline from the Blues match. Nanai-Williams will also cover centre.

It's a different story up front where half the starting pack changes, including both props.

Ben Afeaki has been ruled out with the concussion suffered in the Blues match and Ben Tameifuna comes back to start at tighthead and Toby Smith replaces Sona Taumalolo at loosehead.

Skipper Craig Clarke returns at lock after missing the Blues match and Tanerau Latimer returns in place of Sam Cane on the openside flank.

Rennie said Afeaki still had some symptoms of his concussion this week and they were not willing to risk him.

"Once the symptoms die down and he gets a decent week of training in, then we'll consider him in the mix again."

As far as Latimer being preferred to Cane as the starting openside, Rennie said Latimer was the fresher player after Cane had a big game for the All Blacks last weekend and both would get opportunities to start over the next two or three weeks.

"Then we'll make a decision as to who gets the big games in the playoffs.

"There's not much between them."

Rennie said his players had come back from their break "really fresh" with lots of intensity and enthusiasm in their training. "We tested the guys and they all recorded they were in their best nick, and some guys have come back and done pb's in strength and speed and so on, so that's really good and we need to put that on the field on Friday," he said.

CHIEFS: Robbie Robinson, Tim Nanai-Williams, Jackson Willison, Sonny Bill Williams, Asaeli Tikoirotuma, Aaron Cruden, Tawera Kerr-Barlow, Kane Thompson, Tanerau Latimer, Liam Messam, Brodie Retallick, Craig Clarke (c), Ben Tameifuna, Mahonri Schwalger, Toby Smith. Reserves: Hika Elliot, Sona Taumalolo, Michael Fitzgerald, Sam Cane, Brendon Leonard, Andrew Horrell, Lelia Masaga.

- © Fairfax NZ News