Austin - World Champion Marc Marquez dominated practice on Friday for the Grand Prix of the Americas, signalling his intent for Sunday in his return to the site of his first MotoGP win.
The 21-year-old Spaniard -- whose victory in Austin last year made him the youngest rider to win a MotoGP race and launched him on his precocious championship charge -- ended the second free practice of the day with a 1.005sec margin over Andrea Dovizioso, with Dani Pedrosa third-fastest.
After topping the first practice with a time of 2min 04.704sec, Marquez set the day's best time in the afternoon of 2min 03.490sec.
He established himself as the favorite to repeat his pole position of last year in Saturday's qualifying.
Honda's Marquez posted his best Friday time on a hard tyre and was less than 0.5sec from his own pole record set on a medium tyre in 2013.
Ducati's Dovizioso led the rest of the pack, using a softer tyre. Marquez's Honda teammate Pedrosa was 1.133sec off the leader's pace.
Italy's Andrea Iannone of Pramac Racing posted the fourth-fastest time.
The best of the Yamaha riders was nine-time world champion Valentino Rossi, who is eager to improve on a disappointing sixth-place finish here last year. Rossi trailed Marquez by 1.3sec.