The Serbian will next face top seed Tsitsipas or Koepfer
The Serbian, who also advanced to the last eight on home soil in Belgrade (l. to Berrettini) and Munich (l. to Struff) this year, hit nine aces and won 73 per cent (47/64) of his first-service points to defeat the former World No. 16 in two hours and 25 minutes.
The 29-year-old reached the quarter-finals in Hamburg in 2019 in his last appearance at the clay-court ATP 500 event. Krajinovic will next face top-seeded Greek Stefanos Tsitsipas or World No. 59 Dominik Koepfer as he aims to reach a first tour-level semi-final since his run to the last four at the ABN AMRO World Tennis Tournament (l. to Monfils) in Rotterdam last February.