Reigning world champion Marc Marquez will start Sunday's Italian race from his worst ever MotoGP grid position of 13th.

The Repsol Honda star, off the front row just six times since joining the premier-class in 2013, was thwarted by a series of mistakes, tactical errors and technical issues.

It all began when he was pushed out of the practice top ten in FP3, having been preoccupied with electronics work rather than a fast lap time. That forced the Spaniard into the Qualifying 1 session, where the top two riders progress to the Q2 pole position shootout.

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It should have been a formality, but a further shock saw Marquez pushed down to third.

"So today everything went wrong!" began Marquez, speaking in the team hospitality area on Saturday evening. "We can say that we did a mistake in FP3, that I didn't put on a new tyre [at the end]. I used a tyre from yesterday from the beginning until the end because we were thinking too much about working on the electronics. And to work on the electronics you need [many] laps on the tyre.

"So we concentrated on that and then I go to Qualifying 1. In Qualifying 1 I had the confidence to push only on one tyre, but we had another problem."

Marquez had fallen after losing the front at Turn One during final practice and came close to another accident when he again got sideways under braking on his first qualifying lap. He continued for two more laps before pulling into the pits, at which point he held the second and final Q2 transfer place.

But while he and his team watched anxiously from the garage, Yonny Hernandez shot to the top on the soft Open class rear tyre, pushing Marquez to third in the session and leaving him 13th on the grid.

"In qualifying the rear was sliding a lot," Marquez said. "We don't know why but ok this was my feeling and then we check [the data] and it was like that, spinning a lot. I stopped to try to put another tyre but there was not enough time and that was the main problem in Qualifying 1. But the biggest mistake, I repeat, was in FP3."

Marquez confirmed that he had only planned one run during Qualifying 1, which would then allow two new tyres for Qualifying 2.

"In Qualifying 1 we tried to save two tyres for Qualifying 2 and then the plan was to use one tyre in Q1. The thing is that my confidence was good to use only one tyre [in Q1] but we had one problem and for that reason I couldn't improve, couldn't make a fast enough lap to go to Qualifying 2."

Following a poor race last time at Le Mans, Marquez and his team have been chasing solutions to the RCV's aggressive engine character on corner exit, plus sliding on corner entry. But he insists the Qualifying 1 grip issue was unexpected.

"I was pushing like [normal in] a qualifying practice, but for some reason I couldn't find the rear grip. During the weekend I find and it's good but on that exit I couldn't find. And then I stopped and maybe it was my mistake, but we checked on the data and it [the rear grip] was like that. We are trying to find the solution."

Despite his Saturday misery, Marquez - who already trails Valentino Rossi by 33 points in the world championship - remains confident for the race.

"It is true that in this weekend the rhythm for the race I feel good and I feel ready to fight with the top riders," he declared.

"This morning I worked a lot again on the electronics and then this afternoon I tried to work on the set-up. We improve a little bit but still tomorrow in the warm-up we must try something. But a really small difference because with this pace, with this base, I feel good."

While speculation continues as to the cause and cure for the Honda's handling problems, Marquez was quick to dismiss that idea that he should switch back to the 2014 bike, with which he won the opening ten races of last season.

The reason is simple: "We cannot use the 2014 engine".

That is because the MotoGP development freeze requires the same engine specification for an entire season. As a result, this weekend's electronic and set-up changes are a workaround for the powerplant problems.

"We are using more or less the bike like 2014," Marquez added. "Not a big difference. Here during practice I felt good, with good grip. But ok tomorrow we will start 13th so we must start well and try to push from the beginning."

Marquez had hoped that the higher surface grip levels and longer gearing at Mugello, relative to the stop-and-go Le Mans, would in itself ease the 'aggressive' handling.

Marquez may be used to starting near the front in MotoGP, but he also famously won the 2012 Valencia Moto2 round from 33rd on the grid.

LCR's Cal Crutchlow qualified as the top Honda rider in fourth on Saturday, with Marquez's team-mate Dani Pedrosa in seventh.