Shelton’s first career retirement and Tiafoe loss leave US men reeling at Open

• Shelton retires hurt in third-round match

• Tiafoe beaten by qualifier Struff in straights

• Fritz and Paul are last US men still alive

It was a punishing Friday afternoon for American men's tennis as Ben Shelton and Frances Tiafoe were bundled out of the US Open less than an hour apart, leaving only Taylor Fritz and Tommy Paul still standing in the singles draw.

Shelton, the No 6 seed and one of the leading contenders to end the United States' 22-year wait for a men's grand slam champion, was forced to retire from his third-round match against France's Adrian Mannarino with a shoulder injury. It was the 22-year-old's first career retirement, coming as he led by two sets to one before disaster struck late in the third.