Home favourite and top seed Alexander Zverev would definitely want to forget about Wednesday as he fell to a shocking defeat against Norway's Holger Rune.
It will be the sixth time Opelka and Isner meet and the match promises to be a fine encounter of youth against experience.
Cristian Garin is one of the more consistent players on the ATP tour, meaning he has faced off against numerous top stars.
Matteo Berrettini became the first Italian man to reach a grand slam final since Adriano Panatta won the 1976 Roland Garros title.
Garin became the youngest Chilean player to win an ATP Tour match when he defeated Dusan Lajovic in the first round of the 2013 VTR Open
Cristian Garin became the youngest Chilean tennis player to win an ATP Tour match when he defeated Dusan Lajovic.
Cristian Garin is a professional tennis player from Chile. The Association of Tennis Professionals (ATP) has him ranked as high as world No. 17 in singles, which he first achieved ...
The Russian wins his match in straight sets to set up a mouth-watering last-eight date with Stefanos Tsitsipas.
Both Isner and Garin needed three sets to enter the quarterfinals of the Madrid Open.