Joubert said he was disappointed others didn't attempt the jump, and applauded Lysacek's gumption.
"He did a lot of mistakes in practice but he tried it so, it was good for him," Joubert said.
Less than a point ahead of Lysacek is Johnny Weir, who was dethroned by Lysacek at Nationals in January. Weir had a miscue on his triple flip, just past the halfway point in his program and seemed to run out of gas and lose his way in his straightline step sequence.
"My performance today was just OK," said Weir. "This wasn't as crummy as it could have been ... one good dinner and some sleep and I'll be ready to go."
Short programs have bedeviled Lysacek over the last several seasons. He seemed to shake off his problems at Nationals only to have them surface again a month later at the Four Continents Championships.
Adding the quad to his short program was "a risk I had to take even though it was a big one to put it in the short."
But by rushing the jump, he had to place his hand on the ice to steady his landing.
"I said, 'OK, forget about it,' even though that's difficult to do that. The other elements are equally as difficult even though they're not as new," he said. "I had to bring my concentration back just as if I had landed it perfectly."
The men's long program is tomorrow evening.
The Sun's Candus Thomson will file daily reports from the World Figure Skating Championships in Tokyo.