Lleyton Hewitt's bid to make a tournament-winning return to action ended when he was knocked out of the US Men's Clay Court Championships in the quarter-finals.
Defending champion Hewitt, who had hip surgery at the end of January, received a bye in the first round of the competition at Houston's River Oaks Country Club and saw off India's Somdev Dewarman to reach the last eight.
However, the fourth seed was no match for Argentina's Juan Ignacio Chela, only showing glimpses of his old form at the end of each set in the 6-4 6-3 defeat.
Chela served for the match at 5-0 in the second set but was made to wait for victory as Hewitt reeled off three straight games in a comeback attempt.
However, the Argentinean regained his composure though and broke the Australian's serve for the fifth time to secure victory in one hour and 12 minutes and set up an all-Argentinean semi-final clash.
Horacis Zeballos will be Chela's opponent, after the sixth seed sprung a surprise by knocking out top seed Fernando Gonzalez in straight sets, 6-4 6-4.
The other semi-final will be an all-American affair after Sam Querrey and Wayne Odesnik progressed.
Third seed Querrey reached the last four with a 6-3 3-6 6-4 defeat of Chile's Nicolas Massu, converting three of seven break point opportunities to seal victory in one hour and 50 minutes.
Odesnik, runner up in this competition last year, beat Belgium's Xavier Malisse 6-4 6-1 in one hour and 22 minutes.
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