He had to win the San Marino Grand Prix and squeeze the points gap to tenacious young rival Marc Marquez.
Lorenzo delivered as only he can, with a masterclass of stunning, front-running speed to lead all 28 laps with an inch-perfect performance.
His fifth win of the season — now equal on that stat with Marquez — also delivered a debut victory for the seamless shift gearbox fitted to his factory M1 for the first time.
With five races of an 18 race season remaining Lorenzo knows he has to keep it up and add to his back-to-back wins at Silverstone and Misano.
“If I want to win the championship I have to win races and that is the only thing I can do,” Lorenzo said.
“Marc is really strong, he is always in first or second place, so he is really the rider to beat but I have to keep trying and that is what I am going to do.”
Lorenzo was uncompromising as he upped the stakes in the championship chase, refusing to concede that it is all over.
Marquez’s brilliant comeback ride to finish second at Misano, carving up Valentino Rossi and Dani Pedrosa in the process, protected his solid points lead.
After 13 races Marquez has 253 points, 34 clear of Lorenzo who is level at 219 with Pedrosa whose title hopes are fading as he struggles to contain his Honda teammate Marquez.
Lorenzo has unshakeable faith in his bold race strategy. Make a lighting start, lead in turn one and then put the hammer down and open a gap — and dare his rivals to try and run him down.
He staged a brutal assault at Misano which his Yamaha teammate Valentino Rossi described as “fantastic.”
He lead by 1.2s after one lap and pulled the gap out to a race winning cushion of 2.2s after three laps.
Lorenzo led every lap and posted his fastest time of the race on lap three. Everyone else, including Rossi, Pedrosa and Marquez were racing for second.
“With the big advantage I had at the beginning of the race I just had to stay concentrated and not make a mistake because Dani and Marc were really strong and on the same pace as me,” Lorenzo said.
“It was very physically demanding race.
“Five victories is a lot to be still in second place in the championship but I made a mistake in Assen and also Germany, so it my own fault.
“The past is the past and I cannot change it. We need to look to the future, improve the bike and win in the next grand prix.”
While Lorenzo was untouchable out front in front it was Marquez who engaged firstly Rossi, and Pedrosa, in close combat to recover from an early mistake which dropped him to fourth.
His final, forceful overtake to secure second 10 laps from the finish showed again that Marquez holds no fear of reputations, nor the now faded status of Pedrosa as team leader at Repsol Honda.
Marquez struggled on a full fuel load at the beginning of the race and despite his two mistakes that cost time and energy he admitted that Lorenzo deserved this win.
“You never know, but for sure without the mistakes I could have been closer to Jorge at the finish,” Marquez said.
“But today he was stronger, especially in the first five laps. He did a perfect race and I finished second so he deserves the 25 points.”