If it isn't hard to guess who will come away as the 2009 MCE British Superbike Champion, then the greater challenge is surely predicting who will be on the grid from race-to-race?

Leon Camier and Airwaves Yamaha may be romping away to the title following their imperious performance this season - save for Camier's blip at Cadwell Park -, but the 'musical chairs' behind him have almost been as interesting.

Indeed, rider changes have been a constant fixture throughout the season, but this weekend's round at Croft signals arguably the strongest field of the year so far.

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The most notable appearance is that of double champion Ryuichi Kiyonari, who returns to his former HM Plant Honda team to try and boost their 2009 total following a series of rider changes brought on by injury (Glen Richards) and suspension (Josh Brookes).

The move is also a chance for the World Superbike rider to regain some confidence following a series of disappointing recent performances on the Ten Kate Honda that haven't lived up to the promise of his multiple race winning debut year in the category.

While some see this as a prelude to a potential full-time return in 2010, Havier Beltran's insists the motivation behind calling upon Kiyonari was that fellow WSBK alumni Karl Muggeridge was unavailable to race at Croft. Nonetheless, his reappearance certainly brings some star quality to the grid and is likely to provide Camier, who could be heading in the other direction next year, a good test for his capabilities.

Kiyonari's arrival goes some way to overshadowing the return of Brookes too, the Australian making a cautious return to action following the two-race suspension for his Mallory Park faux pas. Desperate to put the accident behind him, Brookes had been gathering some momentum in his quest to hunt down Camier prior to the incident, although it remains to be seen how much the break will have interrupted his progress.

Honda counterparts Hydrex have also undergone a change for Croft, with Karl Harris' being dropped in favour of Tommy Hill. Hill was considered an obvious choice for the team following the announcement that Harris had been released from his contract, the former BSB race winner having impressed on his brief outing with the Worx Crescent Suzuki team earlier in the season.

He faces a challenge though, with Harris' fourth place in the standings having not been good enough for the ambitious team. As such, Hill will be expected to get close to Stuart Easton if he is to see out the season with them.

Harris, meanwhile, has landed at Rob Mac Yamaha once again, the 'Bomber' being drafted in to compete on the Node4-branded machine in place of Jon Kirkham, who is still struggling to overcome hand injuries.

If anything, the various movements and high-profile returnees could overshadow the fact that Camier is expected to move into 'match point' position at Croft. Fifteen wins and a margin over almost three figures over James Ellison would indicate that this is his title to lose, but it shouldn't diminish his achievements, which could see him continue to raise the bar for predecessors wishing to tackle his awesome victory tally in seasons to come.

Third place Easton is still in with a shout of the title too, but is on the cusp of mathematically falling out of contention this weekend. The diminutive Scot has shown great pace, particularly off the startline, but he remains winless in a season where he has led a large proportion of the races.

With the top three spaced out, attention instead turns to the battle for fourth position in the standings, which now sees fourth to eighth covered by just 7.5 points. Harris leads the way, but he has a new bike and team to reconnect with this weekend, giving Simon Andrews, Julien Da Costa, Ian Lowry and Chris Walker a good shot at usurping him.

The performance of the re-branded Confused.com Kawasakis has been a major talking point this season, and while Andrews grabbed the headlines with his maiden podium at Cadwell Park, the increasingly consistent Da Costa is shadowing him all the way. Given the team were targeting top five race results this season, their current fifth and sixth in the overall standings is a remarkable achievement.

Lowry has also starred, the Ulsterman briefly holding fourth between the races at Cadwell Park, despite the fact he has finished in that position just once this year. The ever-present Walker remains in contention too, meaning any slip from these riders is likely to result in a different looking leaderboard come Sunday evening.

Elsewhere, John Laverty continues on the ascension, the reigning Cup champion enjoying a boon in his form recently with a front row starting position at Cadwell Park and three top five results in the last six races. He is currently tussling in the standings with Sylvain Guintoli, who continues his return from injury with a less arduous venue in Croft this time around.

One rider who will be missing from the grid, however, will be Graeme Gowland, who his suffering from the injury picked up at the previous round, while Howie Mainwaring will appear on the Maxxis Adept Yamaha again following the confirmation that David Johnson has been released from his contract.

Over in the Cup championship, Gary Mason is poised to wrap up the title should he continue his winning streak and closest rival Peter Hickman endures a bad weekend. Like Camier, Mason's title win is almost a formality and, should he be crowned at Croft, he'll have beaten his championship class opposite to the first title win of the season.