This was the world No.1's 17th consecutive win to start the year — the best such run of his career — but no previous opponent has tested him like Coric did in California.

Indeed, the No.49 21-year-old looked well on course for a major scalp as a run of five consecutive games saw him take the first set and break to open up a lead in the second as he closed in on just a fourth ATP Tour final.

But a few errors crept into Coric's game, the likes of which Federer routinely punishes, and a commanding lead was gone in a flash as the No.1 seed turned the match on its head with consecutive breaks to level the contest.

Federer then came from behind to edge the third set of a compelling match and ensure there would be no repeat of Simona Halep's shock exit in the women's draw, with either Milos Raonic or Juan Martin del Potro now next up in the final.

The pair was evenly matched at the start of the first set, comfortably holding serve until, at 5-5, the underdog ramped up the pressure and broke Federer at the second attempt, allowing him to clinch the set in the next game after an erroneous call had initially denied him a perfectly good winner.

The Croatian broke Federer's serve in the first game of the second set, too, before maintaining control as he came charging back from 40-0 down to save the three break points and hold serve to make it 3-1.

Coric appeared to have a response to everything as he again rescued a break point in his next service game but, roared on by a partisan crowd, it was third time lucky for Federer, who levelled the set at 4-4 and then ruthlessly punished the reeling youngster when he next served to take the match to a decider.

It looked as though the pendulum had swung again when Coric broke the Swiss to love in the opening game of the third, but back came Federer to draw level after a magnificent point in the second game.

Although Coric's resolve remained and he kicked on again to break again and lead 4-3, a double-fault allowed Federer to level matters and the veteran ultimately outlasted his opponent as he served to stay in the match, nervy errors ending the unseeded talent's fight in the first of three match points.

"I got a bit lucky," Federer conceded on court, but he certainly earned a slice of fortune after a historic start to the season.