The ballet revolves around him, almost as if he were conjuring the other characters. In one sequence, he illustrates the brilliance with which he shapes and colors movement: He stretches and retracts, allowing a ripple to undulate through his body, then initiates a series of turns, going faster, then slower, then faster again. He seems to respond to messages locked in the music, creating a character even when there is no actual story.

“I see him as a hero,” Ms. Tharp said during a rehearsal break, “something that’s out of vogue these days. And heroes are always, to a certain extent, alone.”

Ms. Tharp knows him well, having spotted him early on and given him a central role in her 2000 ballet “The Brahms-Haydn Variations” when he was still in the corps. “She was the first choreographer to choose me for a principal role simply because she thought I deserved it,” he said.

Though his talent was recognized at a very young age and his rise through the ranks was quick — he was promoted to soloist at 19, after just one year in the company, and to the top rank three years later — it took several more years for him to be assigned the roles he craved and felt he deserved. Those were the dashing romantic leads — princes, warriors, lotharios — who hold together the stories of the great classical ballets. At 5-foot-6, Mr. Cornejo is several inches shorter than the long-limbed standard for male dancers cast in these parts, and it took Kevin McKenzie, the artistic director of Ballet Theater, a while to see him in this light.