Maria Sharapova had spent almost the entire practice session being schooled on her service action and, lo and behold, that vital piece of her armoury crumbled yesterday as the second No 1 seed of the Pacific Life Open disappeared before the tournament reached the period when the cream ought to rise to the top.

Two days after Roger Federer bit the desert dust, so Sharapova was gone, beaten 4-6, 7-5 6-1 by Vera Zvonareva, her fellow Russian, who has often managed to get beneath the US Open champion’s skin. Here, too, was a prime example of the Sony Ericsson WTA Tour’s on-court coaching initiative in its element.

A coach can be summoned at the end of each set and, if an opponent is having a medical time-out, they are entitled to go on court again. Samuel Sumyk in the Zvonareva corner and Michael Joyce, a hitting partner in Sharapova’s, were both on court at the end of the first and second sets — and the upshot is that Sumyk should be getting a raise.

Whatever words of inspiration he used, the response from the world No 20 against the defending champion was immense as, from 5-3 down in the second set, she lost one of the remaining 11 games to secure a place in the quarterfinals against Li Na, of China, who was similarly impressive in a straight-sets victory over Jelena Jankovic, the No 7 seed.

The sharp end of Sharapova’s defeat was littered with double faults, 13 in all. It could not have helped that, in practice, she was being urged into subtle ball-toss and racket speed trajectory changes that probably played on her mind in the match.

Jamie Murray and Eric Butorac were going out of the doubles after a super tie-break defeat by Julian Knowle and Jürgen Melzer, the Austrian pair, but Murray’s consolation is a debut place in the Davis Cup side to face the Netherlands next month in Birmingham. Murray’s younger brother, Andy, and Tim Henman, who will both be in the Great Britain team, reached the quarter-finals of the doubles.

John Lloyd, the Britain captain, has also promised a place to Greg Rusedski, who played for the first time in four months yesterday, losing in a Challenger first round in Sarajevo.