Reigning 250cc world champion Marco Simoncelli is hoping to be in the top five during his World Superbike debut at Imola this weekend.

After a successful two-day test earlier this week at Mugello, Simoncelli was confirmed as racing the factory Aprilia RSV4 - in place of the injured Shinya Nakano and alongside fellow Italian Max Biaggi.

"I did some testing with Aprilia and things went quite well, I hope I can be as quick here," said Simoncelli at Imola on Thursday. "It's clear that it's going to be tough but I must try and do a good job, set the bike up and be as quick as possible in the race.

"My rivals are all strong, starting with Biaggi, and then Spies, Fabrizio, Rea, a load of guys. For sure it'll be a great battle, a satisfactory result for me would be in the top five, it would be like a win!"

Simoncelli is a winner of ten 250 and two 125 grands prix. The 22-year-old Gilera rider, who now has only a slim chance of retaining his crown, will graduate to MotoGP next season with Gresini Honda.

Biaggi - a four-time 250GP world champion, 13 time 500GP/MotoGP race winner and four time WSBK race victor - is happy to have Simoncelli alongside him... providing he's slower!

"It's great that guys like Simoncelli come and race occasionally in Superbike," said Max. "It does their experience and our championship a lot of good. But I won't be as happy for sure if he goes quicker than me!"

Biaggi has taken one win and five podiums with the brand new RSV4 to hold fifth in the standings with three rounds to go.

Imola is returning to the World Superbike calendar for the first time since 2006. A test session on the slightly revised layout was held in July.

Of the 22 WSBK races held so far this season, title leader Ben Spies (Yamaha) has won 12, Noriyuki Haga 6 (Ducati), Jonathan Rea 2 (Honda), Michel Fabrizio 1 (Ducati) and Biaggi 1(Aprilia).