France's Julian Alaphilippe took the overall lead in the
The 22-year-old Alaphilippe, riding for Etixx-Quick Step, bolted to the front with 2 1/2 miles left and completed the 80-mile leg from Ontario to Mount Baldy ski resort in 3 hours 42 minutes 13 seconds.
Sagan, who has 13 career Tour of California wins, fell of his bike just after the finish line. He dropped 2 seconds behind Alaphilippe in the overall standings with one stage left.
"It was very hard and very long," said Alaphilippe, who claimed his first victory this season and the fifth of his career. "In the last 15 miles there was a break and then there was only a small group for the last climb.
Alaphilippe finished third in Stages 3 and 6. Earlier this season, he was the runner-up in prestigious Liege-Bastogne-Liege and La Fleche Wallonne one-day races.
"Today I am surprised," Alaphilippe said. "They played with me a little, but in the last kilometers I attacked and stayed away. I went to the full limit in the last mile. It was steep, but I was feeling good."
Colombia's Sergio Luis Haneo Montoya of Sky was second in the stage, 23 seconds behind, to move into third place in the standings — 33 seconds back.
Despite his race lead, Alaphilippe said he would ride in support teammate
"Tomorrow is probably a stage win so I guess I will work for Mark Cavendish," said Alaphilippe, who became the event's fourth race leader. "We have a very strong team so for today I am happy."