Marc Marquez continues to top Austin MotoGP practice for Honda

Already a three-time winner at the Circuit of the Americas, Marquez had dominated Friday's running, but his advantage on Saturday morning was significantly smaller.

He improved on his own overnight benchmark with a time of 2m03.885s early, 0.5425 seconds up on the field at the time.

The fastest laps of the session came in the final four minutes and, on a slightly-used medium rear tyre, Marquez set consecutive times of 2m03.861s, 2m03.839s and finally 2m03.741s to lead the way.

Most of Marquez's closest challengers were on new soft rear tyres, including Ducati's Andrea Iannone, who logged a late 2m03.937s to finish 0.196s behind the Spaniard.

Jorge Lorenzo was third, the Yamaha rider 0.590s down on Marquez but marginally ahead of Suzuki's Maverick Vinales.

Inside the final minute, LCR Honda's Cal Crutchlow jumped up from 13th to third with a time of 2m04.408s, and while he dropped to fifth after the chequered flag, he has still done enough to book a spot in the second phase of qualifying.

Valentino Rossi was sixth, ahead of Dani Pedrosa, Loris Baz and Andrea Dovizioso, who fell at Turn 11 halfway through the session.

Crutchlow's lap bumped fellow Briton Scott Redding out of the top 10, but the Pramac Ducati rider was able to improve at the death to a 2m04.796s to snatch 10th and a Q2 spot from Pol Espargaro by just 0.014s.

Hector Barbara looked set to join Avintia Ducati team-mate Baz inside the top 10, but was hurt by a late visit to pitlane for a suspected brake problem, falling to 13th.

Following his crash in first practice on Friday, secondary x-rays on Saturday morning identified broken bones in Jack Miller's right foot.

The Marc VDS Honda rider persisted through the session with more pain than he felt on Friday, and improved by more than one second on his Friday time and finished 17th.

Bradley Smith's tough start to 2015 continued, with Tech3 Yamaha trying a completely different set-up direction, only for last year's top satellite rider to finish 19th, 2.221s off Marquez's pace.

PRACTICE THREE TIMES