"There are racket smashes, and then there are racket smashes" - Sky Sports commentator Barry Millns summed up Alexander Zverev's rage after losing control during his Shanghai Masters defeat.
"For me, it's impossible to lose a match when I've only been broken one time", Zverev said.
Sixth-seeded Grigor Dimitrov also advanced, but had to save three match points before beating Ryan Harrison 3-6, 6-3, 7-6 (6). "I was feeling good the whole match, even coming out of the first set, which he was playing well".
Del Potro, who won the US Open eight years ago over Roger Federer but has struggled for a long time with multiple wrist surgeries and recovery, lost the 2013 Shanghai final to Novak Djokovic in his best performance at the event.
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Dimitrov, chasing a spot at the season-ending ATP Finals in London, beat American Sam Querrey to set up a Chinese reunion with Nadal.
The German prodigy and the 29-year-old, whose career has been beset by injury, went toe to toe in the second set and the tie break was just as tight until Del Potro grabbed the crucial mini-break.
Zverev's fury at letting the match slip became apparent in the third as he massacred his racquet as the Argentine broke for a 3-2 lead in the decider. "I just had to find my way through the whole match". "He's still very young and has to keep learning".
Fourth seed Marin Cilic and Spain's Albert Ramos-Vinolas go head to head in the other quarter-final.