Champion five-year-old California Chrome raised the roof at Del Mar when he fought out a thrilling finish to the G2 San Diego Handicap in his first appearance since his World Cup win in Dubai in March.

The clash between California Chrome and his high class rival Dortmund lived up to the hype as pair engaged in terrific battle from the home turn.

Dortmund was a half-length behind the 2014 Horse of the Year on the turn but the hulking son of Big Brown found more on the inside as the pair duelled to the wire.

California Chrome eventually outlasted his rival to win by a half-length.

"I tell you, Dortmund made him work for it," said California Chrome’s trainer Art Sherman.

"Dortmund is a really game horse. I think both horses needed a race and you'll see two stronger horses coming back in the Pacific Classic."

That potential matchup in Del Mar’s summer feature next month, along with the presence of defending champion Beholder, could set up one of the most significant races in the California track's history.

Dortmund, ridden by Gary Stevens, took up the early lead while California Chrome and Victor Espinoza stalked him in second.

Dortmund had a 1.5 length lead in the backstretch before California Chrome moved up to challenge and head him entering the final turn.

"I saved something for the end. I knew I'd have to," Espinoza said. "I have a lot of respect for Dortmund and he made me run hard.

“This horse was carrying a lot of weight. That was the challenge but he was a runner all the way today.

“What a terrific comeback race for him. He’s such a special horse.

“He showed everyone just how special he is."

Stevens said the race went to plan early but then became a real pressure test.

"We had the slow fractions I was hoping for and he was going along fine. Then from the three-eighths it was on.

“I thought maybe we were going to run out of gas but he kept digging. He ran that last quarter mile on heart.

“A terrific comeback race from him. He’s some horse.”

Multiple G1 winner Dortmund had been off the scene since winning at Del Mar last November.