San Francisco Frontiers - Marquez brothers sizzle in practice for MotoGP season opener

Older sibling Marc, who has joined double world champion Francesco Bagnaia at the Ducati factory team, was fastest in morning practice in fierce temperatures.

The 32-year-old Spanish great looked poised to top the timesheets in the afternoon too, until Alex clocked a leading lap of one minute and 29.020 seconds on his Ducati late in the session.

That relegated the more acclaimed Marc into second by just 0.052secs.

But Italy's Bagnaia struggled badly -- 10th in first practice and a lowly 13th in the second.

He was left furious after compatriot and friend Franco Morbidelli, who came fifth, held Bagnaia up as the former world champion attempted to improve his time.

Spain's Pedro Acosta was third-quickest for KTM.

The first points of the campaign are up for grabs in a 13-lap sprint race on Saturday, before the main event at Buriram on Sunday.

Marc Marquez and Bagnaia have been hailed as a dream team but some observers have cautioned that the high-octane mix of two fast high-profile racers could prove too combustible over the 22-race season.

Marquez enjoyed a strong pre-season on his new bike, having joined Ducati from Honda, and is strongly fancied to win a first world crown since 2019.

The start of the new MotoGP season has been overshadowed by the absence of world champion Jorge Martin.

The Spaniard suffered fractures to his right hand and left foot in a horror crash during pre-season testing in Malaysia.

Then his Aprilia team said this week that Martin suffered another mishap in training and had to have more surgery.

Aprilia now say he will miss both Buriram and the next race, in Argentina in mid-March.

Z.Sanchez--SFF