Grant Holloway's bid for a fourth consecutive world 110m hurdles title came crashing to a halt when he could only finish sixth in his semifinal in Tokyo on Tuesday.
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The Olympic champion, 27, has not been his dominant self this season, and it showed at Tokyo's National Stadium.
The American enjoyed a good start, but floundered badly in the closing 30 metres in a semifinal won by Jamaican Tyler Mason in 13.12sec.
Holloway's US teammate Cordell Tinch has undeniably been the class act of the season.
He advanced to the final scheduled for 1320 GMT along with Japan's Rachid Muratake – a finalist at last year's Paris Olympics who is hitting his strides at just the right time.