Germany's Tommy Haas rallied to beat top seed and defending champion Andy Roddick 6-7 (1-7), 6-4, 6-4 in the quarter-finals of the U.S. Clay Court championships on Friday.
The fifth seed needed two hours and 11 minutes to see off Roddick and advance to his fourth semi-final of the year.
It was a rare defeat on Houston clay for Roddick, who has claimed the title three times and came into the match with a record of 25-2 in the event.
Haas, who beat Roddick in the 2004 final, will next meet American wildcard Mardy Fish in Saturday's semis.
Fish also needed to rally from a set down to dispose of compatriot Vince Spadea 4-6, 7-6 (7-1), 6-2.
It will mark Fish's first semi-final appearance since 2004 in Halle where he lost to Germany's Rainer Schuettler.
Seventh seed Paul Goldstein reached his second semi-final of the year with a tidy 6-3, 6-4 win over the Spain's Albert Montanes.
The 29-year-old American needed 78 minutes to ease past the Spaniard to move within one win of reaching his first career final.
Goldstein will next meet Austria's Jurgen Melzer, who booked his semi-final place with a 7-5, 6-4 win over Spain's Fernando Vicente.
"Today's match against a guy who grew up on clay for me is a great effort," said Goldstein. "It's one of my better wins.
"For a guy who's more comfortable on hard courts to beat a Spanish guy who loves the clay is a very satisfying win."
