MOTEGI, Japan, Sept 27 (Reuters) - Twice MotoGP champion Francesco Bagnaia roared back to form as he won the Japanese Grand Prix sprint from pole position on Saturday, while his Ducati teammate Marc Marquez put himself within touching distance of a seventh MotoGP title by coming second.

Bagnaia made a blistering start, quickly building a comfortable lead and crossing the line well ahead of Marquez, whose brother and closest championship contender Alex finished outside the points in 10th place.

Marc Marquez stretched his lead over Alex in the riders' standings by a whopping 191 points. The 32-year-old Spaniard can win the title in Motegi on Sunday if he does not concede more than six points to his younger sibling.

"I was losing time, and then I saw that Pecco (went) away, and I decided just to try to do my race. And then when I was in front, the pace was good, the feeling every time is better and better," Marquez said.

"Tomorrow will be a long race, but we cannot forget that our main target this weekend is another one."

Bagnaia, who trails Marquez by 272 points, was visibly moved after securing his first sprint win of the season.

"I'm back to do my favourite races -- starting well and pushing, not fighting behind," the Italian said. "I'm super happy. I want to say thanks to the team that, like always, have done an incredible job to set to me, finally, a fantastic bike.

"I was able to push, I was able to control, and it's super sweet, these emotions, so super happy."

KTM's Pedro Acosta, who had qualified fourth, came third ahead of fellow Spaniard Joan Mir to round out the podium. Acosta, 21, briefly claimed second place but was overtaken by Marquez with two laps remaining.

MARTIN SUFFERS ANOTHER BLOW

Reigning MotoGP champion Jorge Martin's nightmare season continued as the 27-year-old Spaniard collided with Aprilia teammate Marco Bezzecchi on the opening lap, having started 17th on the grid.

MotoGP later confirmed that Martin, who has already missed 10 races this season due to injuries, is ruled out of Sunday's race after X-rays revealed a displaced fracture of his right collarbone.

"The rider will be transferred by helicopter to the Dokkyo Medical University Hospital for a CT scan to make the best assessment of the situation," Aprilia said in a statement.

Italian Bezzecchi, meanwhile, is undergoing medical checks to his right leg.

Reporting by Pearl Josephine Nazare in Bengaluru; Editing by Kim Coghill

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Bagnaia regains form with Japanese GP sprint win, Marquez on brink of title