Less than a month ago, you would have been forgiven for thinking that this year's World Superbike Championship was destined for just one rider: Troy Bayliss.

A strong, consistent start to the season had been enough to establish a seemingly infallible margin of error for the Australian in his final year of racing as he galloped away while others struggled to string a similarly impressive run of finishes together.

And yet four races later and the situation is looking rather more competitive as Carlos Checa and Max Neukirchner chip away at Bayliss' seemingly unbreakable fa?ade.

Even then, it took Checa a double win in the USA to get himself into contention, while there are still some people waiting for Neukirchner to trip up in what has been an outstanding season so far.

On top of that, as the series heads south for the San Marino round at Misano, the title fight has arguably expanded to accommodate a fourth rider after 'Nitro' Noriyuki Haga performed a remarkable double victory at the Nurburgring.

All the more significant given his injury woes, Haga's superb performance in Germany has propelled him well into the title fight that looks like it really could go any which way between Ducati, Honda, Suzuki or Yamaha.

Bayliss still holds a comfortable margin though of 39 points, a lead that would be considered quite dominant if it hadn't been almost double that just before World Superbikes went to the USA.

However, while another bad round could make all the difference for Bayliss, the omens are stacking in his favour around Misano, one of the home circuits for the Ducati Xerox outfit. His statistics around the circuit make some ominous reading for his rivals: Ten starts, nine podiums, six wins.

Furthermore, Ducati have won 25 of the 32 races they have competed in there, ensuring this is likely to be a race that is theirs to lose. Not that Bayliss' rivals won't be trying their utmost to avoid a repeat of his double victory from 2007...

Leading that charge will be Checa, who has set himself the target of improving his poor starts this weekend following a frustrating outing at the Nurburgring in which he failed to capitalise on his renewed form. However, Honda didn't have the best bike there last year and with Checa currently the only rider in their portfolio gunning for regular victories, the pressure is certainly on him this weekend.

Pressure is something Neukirchner dealt with admirably when the World Superbikes came to his home ground at the Nurburgring, the German taking pole position and following it up with a pair of podiums. Although his race pace was slightly more disappointing, Neukirchner's sheer consistency at the head of the field is keeping him well in contention and as the only rider seemingly able to get the best from the Suzuki recently, he is likely to be well up for a race win challenge this weekend.

The ever spectacular Haga lived up to his reputation in Germany with a hard-fought double victory that belied the fact he had been under the knife just a few days earlier to repair a broken collarbone. Nonetheless, with the Yamaha coming good around the twisting Nurburgring circuit, Haga was in imperious form as he diced tooth-and-nail with Bayliss and Troy Corser for wins three and four of the season. The only rider to get close to Bayliss on overall wins this year, Haga now needs the consistency to sustain a proper title challenge

Corser came remarkably close to his first win of the season in Germany, only for rain to intervene, but the Australian will take heart from the fact that he is now beginning to challenge at the head of the field regularly and after finishing second at Misano in 2007, he will no doubt be looking to go just one better this time around.

Just slipping out of contention now is Fonsi Nieto, whose strong start to the season has started to become a distant memory for the Spaniard. An eighth and ninth place finish in Germany will have done little steady those nerves, while qualifying is now starting to become a major bugbear for him.

On the plus side, he is closer to the fight for second in the championship than he is to those in the lower reaches of the top ten, with that gaggle being led by Ruben Xaus.

The first of the riders who were perhaps expected to be doing slightly better at this stage in the season, Xaus didn't warm to Misano last year, but is quite capable of presenting a more sustained challenge this time. The same could be said for Sterilgarda team-mate Max Biaggi, who has had a frustrating season thus far

Having begun showing glimpses of pace comparable to Bayliss, Michel Fabrizio will be looking for more podiums - and maybe even a win - this weekend on the bike that is, arguably, the best suited to the circuit. You could say that his future depends on it...

Effectively a home round for Ryuichi Kiyonari, who doesn't live too far away from the area, the Japanese rider is desperate for a better showing after decent race pace in recent rounds has been ignored courtesy of lowly starting positions that have left him too much to do come race day.

Elsewhere, countryman Yukio Kagayama is back in action after the fall that ruled him out of the German round, while Gregorio Lavilla will look to keep his points ticking over in a week that has speculated he may be due for a shock return to the British championship sooner rather than later.

Others to look out for this weekend will be Lorenzo Lanzi, who performed well at Misano last season, as well as Roberto Rolfo, who had a top five result too.

PSG-1 Kawasaki are also chasing an improvement in results at Misano, which acts as the San Marino-based team's home round. After a decent top ten showing at the Nurburgring, the top five now beckons for Regis Laconi and Makoto Tamada.

Finally, the World Superbike Championship welcomes back Luca Morelli and says hello to Norino Brignola. Morelli, who was dropped by Alto Evolution Honda earlier this year, will see out the season with D.F. Racing after Russell Holland decided to step down to Supersport instead. Brignola, meanwhile, makes his WSBK debut aboard the Grillini Yamaha in place of the axed Loic Napoleone.