Feliciano Lopez of Spain advanced to the semifinals of the Mercedes Cup in Stuttgart, Germany, by upsetting third-seeded Tomas Berdych of the Czech Republic 6-7 (4), 6-3, 6-4 on Friday.
Zverev double faulted on match point to end it.
Lopez has not featured in a final since losing to Ivo Karlovic in the Los Cabos Open in Mexico in August 2016, and won his last tournament at the Swiss Open the previous month.
The experienced Lopez had earlier edged out German Mischa Zverev in the first semi-final, 6-7 (2/7), 7-6 (7/4), 7-5.
"I think my serve was working quite well in some important points, and that was probably something very important in today's match", Lopez said.
It was a disappointing day for the Zverev family as Mischa's younger brother Alexander lost out in straight sets to Gilles Muller in the semi-finals of the Ricoh Open in s-Hertogenbosch.
The 39-year-old Haas, who defeated Roger Federer in the second round on Wednesday, was playing for the last time at the grass-court tournament, and he was accompanied by his six-year-old daughter Valentina at the post-match news conference, where she sat on his lap.
Ultimately, it was the first set which proved decisive and ended in a tie-break after all 12 games went with serve.
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