Sharks flyhalf Curwin Bosch says former teammate Marius Louw is a danger man ahead of the teams' URC derby a Ellis Park on Saturday.

Midfielder Louw, 27, was on the Sharks' books since 2014 before joining the Lions last year.

He's made a significant impact in Johannesburg and has taken over the captaincy in recent weeks after an injury to lock Reinhard Nothnagel.

"It's strange seeing Marra (Louw) in a different jersey... we started our careers together at the Sharks," Bosch told reporters on Tuesday.

"He is a flippin' great player... he's tough, hard, and any team will get a high work rate and physicality from him. It's just a matter of us stopping that, and minimising or taking his space away."

The Lions have a few former Sharks among their ranks, with the likes of experienced utility forward Willem Alberts, young lock Emile van Heerden and scrumhalf Sanele Nohamba now plying their trade in Johannesburg.

"We know what to expect from the Lions. They like to play an expansive brand of rugby at home when they have the altitude factor in their favour," Bosch added.

"They have some quality players, and obviously a couple of our old boys who will be playing against us. It'll be a good physical and set-piece challenge for us."

The Sharks were thumped 46-19 at home by the Stormers in their last outing. Bosch said they addressed the errors made in that clash.

"That performance was way below our standards, especially at home," said Bosch. "We had an in-depth review of what went wrong and on the day nothing went our way.

"We made mistakes we would not usually make and a good team like the Stormers will punish you for those mistakes.

"We just could not get going because of those errors and our discipline also let us down. We were always on the back foot because of giving away penalties and so it was very hard to get back into the game.

"Starting well is very important for us. We want to get on to the park and start fast, well, and with good execution of our game plan."

The Sharks are eighth (33 points) on the  https://www.unitedrugby.com/match-centre/table/202201" rel="nofollow - URC standings  with seven wins from 12 matches, while the Lions lie 13th (24 points) with five wins from 12 matches.

Saturday's clash at Ellis Park kicks off at 15:00.