Marquez and Lorenzo top the bill in Valencia

A MotoGP season dominated once again by Marc Marquez rolls to a close in Valencia this weekend with a fond farewell for another Spaniard, former champion Jorge Lorenzo who announced his retirement on Thursday.

Marquez has undoubtedly been the star of the season, winning 11 races so far and wrapping up his sixth world title with four races to spare.

No one has come close to his speed and consistency.

Since the Spanish GP in Jerez at the start of May, Marquez has finished either first or second in every race, an achievement that fast-tracked Honda to its eighth constructors' championship, its fourth in a row.

The 26-year-old has done it on the much-maligned RC213V which has been criticised for its handling.

No surprise then to see Marquez planning to use Valencia as something of a test drive for next season.

"We are looking to 2020 already and continuing to try some options while we have this time before we go into test mode after the race," he said.

Surprisingly, given that he has won 55 MotoGPs since joining the circuit in 2013, Marquez has only one victory in 2014 to show for his work in Valencia.

His Honda teammate Lorenzo, by contrast, has won it four times in a distinguished career that saw him crowned world champion three times.

The 32-year-old, though, has not had the best of seasons -- he has mustered just 25 points and sits 19th in the standings.

Lorenzo has never quite come to terms with the awkwardness of the RC213V and his season has been dogged by injuries and falls.

At Assen in June he fractured a spinal vertebrae during a crash in practice, causing him to miss three races.

"This will be my last race in MotoGP and at the end of the race I will retire as a professional racer," he told a press conference on Thursday.

With Lorenzo's departure opening up a seat at Honda, there may be an added zip in the Valencia race as riders try to make an impression, none more so that the Frenchman Johann Zarco whose career appeared to be over until Honda threw him a lifeline with a ride in their shadow team.

British rider Cal Crutchlow and the Japanese Takaaki Nakagami are likely having similar thoughts of an upgrade.

Another Frenchman Fabio Quartararo also wants to lay down a marker for next season.

The 20-year-old Yamaha rider has been the revelation of the year and after five pole positions, six podiums and four second-places, it would set up the 2020 season nicely if he were to take the chequered flag for the first time.

"I've won four races at the Ricardo Tormo circuit in the Spanish championship and it's the first place I ever got to ride a MotoGP bike, so there's plenty of good memories in Valencia," said Quartararo.

Valentino Rossi, showing no signs of wanting to retire at the age of 40, will also be pressing alongside Maverick Vinales and Andrea Dovizioso, who finishes second in the championship behind Marquez for the third year running.

Another Spaniard Iker Lecuona makes his debut in MotoGP this weekend. The 19-year-old slides into the KTM Tech team in place of Miguel Oliveira, who was injured in the last race in Australia.

In Moto2, Alex Marquez -- brother of Marc -- has already wrapped up the title leaving a battle for second between the South African Brad Binder and the Swiss Thomas Luthi as the main attraction.

Lorenzo Dalla Porta has already secured the Moto3 title but the MotoE championship has still to be decided with the Italian Matteo Ferrari holding a 19-point advantage over the Spaniard Hector Garzo.