Maverick Vinales survived a high-speed crash to maintain his iron grip on the Qatar MotoGP on Friday, finishing the second day of practice comfortably the fastest man on the track.

The 22-year-old Spaniard, who had already dominated under the Losail floodlights in Thursday's opening session, clocked a best time of 1min 54.316sec on his Yamaha to lead Suzuki's Andrea Iannone (0.532sec behind) and Honda's defending world champion Marc Marquez (0.596).

Nine-time world champion Valentino Rossi, the Yamaha teammate of Vinales, struggled for a second day in succession, finishing 10th on the time charts at 1.098sec behind the flying Spaniard.

Former world champion Jorge Lorenzo, who left Yamaha for Ducati at the end of last season, suffered even more, ending in 12th place at 1.145sec off the blistering pace set by Vinales.

Vinales, who moved from Suzuki in the winter before going on to dominate all four pre-season testing sessions, had escaped unscathed from a crash earlier in the day.

The incident happened on Turn Four after he had slipped by Rossi.

Sparks flew from beneath his bike as it careered across the track but Vinales was soon able to resume his evening's work on his back-up machine.

"The crash was a big mistake on my part. I was pushing and I was going wide," explained Vinales.

"I was at that point where you have to decide – to go wide or try and make the corner. I tried to make the corner and I lost the front. My mistake and I was angry with myself because I shouldn't make those mistakes.

"But I'm happy because we had good pace today even though the conditions weren't as good as yesterday. It was slippier, I don't know why but we did 1:56s consistently.

"The bike is working well but we just need to improve the grip a bit. Maybe it was the conditions today after it rained and it was a bit dusty, so let's check tomorrow. I'm happy overall but the crash was a big mistake. I know when I concentrate 100 percent I don't make those mistakes."

Rossi's struggles earlier on Friday led to 1993 world champion Kevin Schwantz suggesting that the great Italian, now 38 years old, may even retire at the end of the season should he be outpaced and outshone by Vinales in the championship.

"Do I think he'll retire at the end of the year if Maverick hands him his ass weekend in, weekend out? He possibly could," Schwantz told motorsport.com.

Sunday's night-time race in Qatar is the first of 17 rounds in the 2017 championship.

However, Rossi can at least boast impressive form at the desert circuit, having won there on four occasions.