Cape Town - The Bulls are happy they won't be facing flyhalf Danny Cipriani when they take on the Rebels in Melbourne on Friday, but believe the Rebels will still pose a big enough threat.

The England flyhalf on Monday parted ways with the Melbourne-based team, four months before his contract was due to end.

The 24-year-old, who has played seven Tests, has been under pressure to hold down the flyhalf spot for the Rebels since the arrival of Wallaby James O'Connor from the Force.

O'Connor is out with a long-term injury after suffering liver damage in their last match against the Waratahs. Both he and Cipriani are players with that sought after X-factor, and Bulls backline coach Pieter Rossouw admitted they are relieved to take the Rebels on without the duo's presence.

"He (Cipriani) was definitely a big play-maker and with O'Connor also not there we have to use the disruption to our advantage," Rossouw told Beeld.

However, Wallaby star Kurtley Beale is still there and expected to start at flyhalf.

Rossouw is also wary of the threat skipper and centre Stirling Mortlock could pose. The 34-year-old hasn't played this Super Rugby season due to ongoing calf problems but was able to get through an intensive running session and is set to lead his team again.

"He ran really well and he'll take part this week, all things being equal," Rebels coach Damien Hill said.

Mortlock is set to replace O'Connor at inside centre, while Mitch Inman will play outside centre after his recovery from a broken hand.

"I'm not sure whether he will be starting or off the bench but he's ticked every box he needs to tick," Hill said.

Rossouw said he expects Mortlock to start. "He is a veteran and even though he is a bit old he's still an exceptional player and will ask some questions."

Bulls coach Frans Ludeke also warned against the threat the Rebels could pose, especially after some lapses on defence in their last game against the Brumbies. "The Rebels are a team that can score some spectacular tries, so we'll have to remain focussed for 80 minutes - especially since they don't stop playing," said Ludeke.

The clash at AAMI Park kicks off at 11:40 (SA time) on Friday.