Waratahs South African half back Sarel Pretorius has told his team mates that they will have to beef up and be more physical if they are to stand a chance of beating the Bulls.

The Waratahs had originally planned to play Daniel Halangahu at inside-centre but in order to beef up the backline they are expected to name Adam Ashley-Cooper in the No.12 jumper and Rob Horne at 13

Halangahu is now expected to start at fullback with Tom Carter and halfback Brendan McKibbin dropping down to the bench.

Waratahs captain and blindside flanker Rocky Elsom is also expected to make his first start of the season while back-rower Chris Alcock should return from injury to give the Tahs more competitiveness at the breakdown.

The front row will however take a blow as Test hooker Tatafu Polota-Nau will be rested after suffering several head knocks, with John Ulugia taking over and new signing Josh Mann-Rea coming onto the bench.

Ashley-Cooper is better known for playing at outside -centre, winger or fullback but he has played international rugby at No.12 and looked comfortable outside five-eighth Berrick Barnes at training this week.

South African Pretorius will be named in the Waratahs starting line-up for the first time in five games is more familiar with the Bulls game and he knows the Waratahs need to stand up against the Bulls and be as physical with the Bulls as they are to their opponents.

"You just have to match them physically and keep contesting. They are quite structured as well, which is based around kicking in the air. "

"So we just have to protect our wingers, and go from there," Pretorius told the Canberra Times.

Berrick Barnes added that you need to take the Bulls head on and keep the scoreboard ticking.

"You've got to score points to beat the Bulls, because they're a side that once they get inside your 22-metre they are very hard to stop, as they always appear to have 130-kilogram players right across the park. "

"But they've leaked their fair share as well. So we're backing ourselves," he said.

Barnes admitted there were a few "ifs" surrounding the Waratahs attack which has been re-jigged.

"It will be a big test for us to see how we gel, as we only have a few sessions before the Bulls match. "

"Still, we've got to change something because what we've been doing hasn't really been coming to fruition. Hopefully on Friday night we can make it work," he said.

Barnes wants the Waratahs to stay adventurous especially after they appeared to be more willing to attack the gain line in Canberra.

"The problem was we'd run from our own half and get to the 50-metre and then turn it over nine times out of 10," he said.

"Silly errors cost us, while their pressure at the breakdown ... became a turning point."