British number one Johanna Konta suffered a shock straight-set defeat by teenager Marketa Vondrousova in the second round at Indian Wells.

World number 11 Konta lost 7-6 (7-5) 6-4 to her Czech 54th-ranked opponent.

She failed to convert four set points in the first set and led 4-2 in the second against 18-year-old Vondrousova.

Konta, 26, has reached just one quarter-final in 2018 and only won eight matches since reaching the 2017 Wimbledon semi-finals.

She was erratic on serve against Vondrousova, landing only 51% of her first serves, and was broken in her opening two service games to fall 3-0 behind.

The Briton recovered to lead 6-5, but then failed to take four chances to win the set on the Czech’s serve and eventually lost it on a tie-break.

She broke serve in the fifth game of the second set for a 3-2 lead – but then lost four games in a row from 4-2 up to concede the match.

Konta’s only quarter-final this season came in Brisbane in the first tournament of 2018, and she also lost in the second round of the Australian Open in January.

Analysis

BBC tennis correspondent Russell Fuller

Konta had plenty of opportunities to win this match – but for all the progress she feels she is making off the court, she lacks conviction on it.

After a ragged start, Konta fought back strongly and had four set points to win the first set before playing a scrappy tie-break with a couple of double faults.

In the second set, she led 4-2 but lost momentum after Vondrousova’s medical time out for a toe problem, and lost the last four games.

Konta’s serve was not a trusty weapon, and she now heads to Miami to defend her title on the back of just one quarter-final appearance in 10 tournaments.