The Reds boss is expecting the host to field a much different squad as they look to avenge for Wednesday's 3-2 loss at Hindmarsh Stadium.

"It will certainly be a different game," he said.

"One thing we won't know is how they'll line up because obviously, they're probably out of the competition now."

"We don't know if they'll rest some players and start concentrating again on the J-League, which I think they play again on the weekend so I think it will be a different game altogether."

One thing Sanfrecce won't know, is what changes Vidmar will make to his own starting 11.

Vidmar indicated he may rest players.

"Yeah I think I will (change the line-up)," he said.

"We just need a little bit of freshness I think."

While the Reds are all but assured a place in the round of 16, Vidmar is still taking a cautious approach to the match.

"The players that have played so far have done a great job. There will be a few there really itching to get out on the park so we'll sit down again on the flight and again tomorrow to finalise what we think is going to be the right team for this game."

Sanfrecce will have to shuffle their formation and line-up with star defender Ilian Stuyanov suspended for the match after seeing red in the match day three clash at Hindmarsh Stadium.

Stuyanov, judged by the referee to be the last man, was expelled after bringing down Matthew Leckie on the half-hour mark.

"Once again we'll probably be a little unsure if they go and change their formation," Vidmar said.

"Up to Wednesday night's game they (had) played with three at the back and they decided to line up with four at the back."

"So with Stuyanov out suspended, we're not sure how they'll line up. They might revert back to what they normally have done in the past or they might stay with the same formation so we'll just have to wait and see."

"We'll have a strategy for both formations."

A freshen-up will greatly benefit the Reds as they showed signs of tiring in the second half of Wednesday night's clash.

Marcos Flores, who was outstanding in the first half, was virtually unsighted after the break as were other members of the squad.

United copped two goals to fall behind 2-1 before the injection of Cassio and Fabian Barbiero, at the expense of two first half standouts, Flores and Lucas Pantelis, swung the game back to United's favour.

"We were a little bit flat in that second half," said Vidmar on Thursday.

"Then I think we showed a lot of urgency. I think the changes we made with Cassio coming in and Fabian, they certainly helped changed the game."

"The game is different here to what he (Flores) is used to in Chile, no question about that. We got him to a point, in terms of his fitness, where we got him there really quickly because he was out of the game for about a month."

"We are just going to have to nurse them, nurture them for the next six weeks... Come pre-season next year these guys will find that extra 15-20 percent."