Roger Federer suffered a surprise defeat to Borna Coric in the final of the Halle Open and will lose his world number one ranking.

Croatia’s Coric, 21, won 7-6 (8-6) 3-6 6-2 to end the Wimbledon champion’s run of 20 consecutive victories on grass.

Federer, 36, was bidding to win the event for the 10th time and secure his 99th career title heading into Wimbledon next week.

The Swiss’ defeat means Rafael Nadal will take over as world number one.

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Coric had claimed his first win over a top-10 player on grass earlier in the week when he knocked out Germany’s Alexander Zverev.

The Croat fended off two set points before clinching the opening set after 57 minutes.

Federer put pressure on Coric’s serve in the second set and converted a break point in the eighth game to force a decider.

Coric then broke Federer in the sixth game of the final set when the Swiss sliced a backhand long, before going on to claim his second ATP title.

Federer, who skipped the clay-court season including the French Open, began his grass season last week by winning the title in Stuttgart.