Updated with more quotes from Valentino Rossi...

Valentino Rossi's hopes of a first home Italian MotoGP victory since 2008 went up in smoke at Mugello on Sunday.

The home star had been supported by yellow smoke from the passionate fans packing the hillsides all weekend. But the sight of white clouds spewing from his factory Yamaha on lap 9 of 23 marked a disastrous second DNF of the season.

The Doctor admitted the outcome was especially disappointing given he had enjoyed his most competitive Mugello showing in years.

Starting from pole for the first time since 2008, when he took the last of seven successive wins, Rossi shadowed team-mate and eventual race winner Jorge Lorenzo from the start - close enough to attack at any moment.

"What can I say? Difficult to say something. I mean is a great shame, is always a great shame when you have a technical failure in the race," Rossi began.

"But this time was also more because we are in Mugello and have a fantastic atmosphere with a lot of fans, and especially because I was very strong all weekend and in the race. I felt good with the bike and was very fast.

"So for sure I can fight for the victory at Mugello that is - more than a target - one of my dreams in the last ten years. Because the last victory was 2008.

"Today in the race I was very fast. And I was behind Lorenzo, but sincerely I think that I had a little bit better pace compared to him, so I can for sure try to attack and try to make my race. But unfortunately the engine broke.

"This one feels very 'heavy', because it was from 2007 that my bike don't break in the race. Nine years.

"Unfortunately on lap six, the bike start to have a problem and the clutch didn't open, maybe because the engine already start to seize a little bit. It is for that reason that I go wide. But in seven-eight corners I was already back on Lorenzo, because I was a little bit faster, but after the engine broke."

Rossi's engine problem wasn't a complete surprise; Lorenzo had suffered what looked like an identical failure in morning warm-up, raising concerns of an inherent design weakness that may be tough for Yamaha to fix given the freeze on engine development.

"I think there was the same thing wrong in both engines, but the big difference is that Lorenzo's happened in the warm-up and for me it happened in the race," Rossi commented.

Mugello has the fastest straight on the MotoGP calendar, with Ducati's Andrea Iannone setting a new all-time top speed record of 354.9km/h (220.5mph) in Sunday's race.

Modifications, for safety purposes, are only allowed if there is unanimous consent among the MSMA MotoGP Commission, which would need to be convinced that the changes offer no performance benefit. But such permission has never previously been granted.

The difficulty is that if a weak part is replaced with a stronger component for example - which then allows the engine to run 'safely' at maximum rpm - that in itself is a performance benefit. 'Just lower the rpm to a safe level', might be a typical response from rival manufacturers.

For such reasons, the example given in the rules is for 'a faulty batch of parts, with supporting documentation from the parts supplier to identify the problem'. If Yamaha's Mugello issues match that precise description they may have a chance of being given permission to change the part.

Both Rossi and Lorenzo began Sunday having 'opened' three of the seven engines allowed for this season, all of which must be of identical spec.

Lorenzo went on to claim his third victory of the season after a last-lap duel with Marc Marquez, and now holds a ten-point lead over the Honda rider. Rossi remains third, but has now dropped 37-points from the top.

"It's a great shame also for the championship, because I take the 'zero' and Lorenzo and Marquez arrive first and second, so now the distance from the top is 37 points. Is very bad. Is quite a big gap," Rossi admitted.

"But I think this weekend I did my job at the maximum. I ride well, I was always concentrating and I arrived ready for fight for the victory in the race. In English they say 'shit happens'! This is today. It is like this, but is very important to be strong and try to take from this bad moment extra energy for the next race in Barcelona."