Last updated on .From the section Tennis

Grigor Dimitrov reached the Australian Open semi-finals in January

US Open Venue: Flushing Meadows, New York Dates: 28 Aug-10 Sept BBC coverage: Live radio and text commentary on selected matches every day.

Seventh seed Grigor Dimitrov lost in straight sets in the US Open second round to Russian 19-year-old Andrey Rublev.

The Bulgarian, 26, was a break up in both of the first two sets but eventually lost 7-5 7-6 (7-3) 6-3 at Flushing Meadows, New York.

Rublev, who beat British number three Aljaz Bedene in round one on Wednesday, will face Bosnia's Damir Dzumhur next.

Czech 15th seed Tomas Berdych lost in four sets to Alexandr Dolgopolov.

The Ukrainian world number 64 triumphed 3-6 6-1 7-6 (7-5) 6-2 as Berdych hit 57 unforced errors, 12 double faults and had a first-serve percentage of only 45%.

Dolgopolov, 28, will face Victor Troicki in the third round after the Serb beat Italy's Stefano Travaglia 7-6 (8-6) 7-5 6-0.

The Ukrainian said on Wednesday he gave his "best effort" in a match at the Winston-Salem Open last week that is being assessed for suspicious betting patterns.

Elsewhere, Austrian sixth seed Dominic Thiem won 6-4 6-4 4-6 7-5 against American Taylor Fritz and will play French 30th seed Adrian Mannarino in the next round.

Gael Monfils, also of France, required five sets to beat American Donald Young 6-3 6-7 (3-7) 6-4 2-6 7-5.

Argentina's Juan Martin del Potro, the 24th seed and 2009 champion, beat Adrian Menendez-Maceiras of Spain 6-2 6-3 7-6 (7-3).

He will face Roberto Bautista Agut next after the Spanish 11th seed beat Dustin Brown 6-1 6-3 7-6 (7-3).

Fellow Spaniard, 31st seed Feliciano Lopez, beat compatriot Fernando Verdasco 6-3 6-2 3-6 6-1 and will play Roger Federer in round three.