Austin (AFP) - Six-time MotoGP world champion Marc Marquez, back in the saddle after recovering from double vision, was sixth fastest in opening practice for the Grand Prix of the Americas on Friday.
Honda star Marquez, chasing an eighth win in nine races at the Austin circuit, was 0.499sec off the leading pace set by France's Johann Zarco on a Ducati who set a session best of 2min 02.542sec.
Australia's Jack Miller, on another Ducati, was second fastest ahead of reigning world champion Fabio Quartararo on a Yamaha.
Ducati's Enea Bastianini, the winner of the season opener in Qatar, was fifth ahead of Suzuki rider Alex Rins, the only man to break Marquez's dominance in Texas when he captured the 2019 edition.
Aleix Espargaro, who won the Argentina Grand Prix last weekend for his first MotoGP triumph in his 200th race, was 11th fastest.
He needs to nip into the top 10 on his Aprilia in Saturday practice to guarantee a spot in the key second qualifying session.
The 32-year-old Spaniard leads the world championship after three races by seven points over South Africa's Brad Binder of KTM and is nine ahead of Bastianini.
Marquez, 29, missed the race in Argentina with double vision following his violent high-side crash in Indonesia in March.
He admitted his numerous falls at the Asian track had left him with a "scary, uncomfortable" injury.
However, he was happy to embrace the enormous risks of the sport.
"I know there is a risk, but it's my passion, I'm here to race and not to think about injuries.Passion, always, is stronger than my injuries," he said Thursday.
"After an injury, the first week you say to yourself 'I don't want to take this risk of MotoGP again and be injured again'.But the week after, this passion, this adrenaline takes over."
