Johanna Konta through to Miami Open fourth round

Johanna Konta continued her timely return to form with a 75-minute rout of Elise Mertens to reach the fourth round of the Miami Open.

The defending champion, whose triumph last year paved the way for a march into the world top 10, faces a slide down the rankings if she fails to repeat the feat.

And Konta has risen impressively to the challenge, building on her first-round win over Kirsten Flipkens with an emphatic 6-2 6-1 win to see off the 22nd seed.

Konta had been pegged back after an early break against Mertens before reeling off four successive games to take the first set in style.

And despite giving up a break herself in the second set, Konta proved clinical in exposing Bertens' problems on serve to seal the match in convincing fashion.

Konta's consistency in Miami will come as a confidence boost for the Briton who has broadly struggled since losing her Wimbledon semi-final to Venus Williams last year.

Hampered by a hip injury, she was beaten early in the Australian Open by lucky loser Bernarda Pera, and also crashed out early in Indian Wells last week.