Roger Federer of Switzerland, Eva Herzigova, Borna Coric of Croatia and tournament director Ralf Weber during day seven of the Gerry Weber Open at Gerry Weber Stadium on June 24, 2018 in Halle, Germany. Thomas Starke/Getty Images

Roger Federer was dealt a blow Sunday in the leadup to Wimbledon, falling to Borna Coric at the Gerry Weber Open final in Halle, Germany, 7-6 (8-6) 3-6 6-2.

It was the second title and the first on grass for the 34th-ranked Coric, a rising star on the ATP tour. The 21-year-old Croat was a revelation on grass, having not dropped a set in the tournament and outlasting Federer in a 57-minute opening set. Coric defeated No. 4 Alexander Zverev in his first match.

The victory could serve as a big momentum builder for Coric, who has just one win at Wimbledon. The Grand Slam starts on July 2.

For Federer, the loss snaps his 20-match winning streak on grass and means he will no longer be the world No. 1. The 36-year-old Swiss legend has been in a tight battle atop the rankings with Rafael Nadal.

Federer, the defending champion of the tournament, was seeking his 10th title in Halle.

Earlier this month Federer held off Milos Raonic to win the Mercedes Cup in Stuttgart, Germany. It was Federer's first tournament in two and a half months and after skipping the French Open for the grass court season.

Federer will be seeking his ninth Wimbledon title next week.