World number five Daniil Medvedev and defending champion Alexander Bublik were both knocked out in the second round of the Halle Open.

Russian Medvedev, the 2021 US Open winner, lost a final set tie-break in a 6-3 2-6 7-6 (7-5) defeat by China's Zhang Zhizhen.

Kazakh Bublik, who defeated Russia's Andrey Rublev in last year's final, was beaten 7-6 (7-5) 4-6 6-3 by American Christopher Eubanks.

Elsewhere, Victoria Azarenka reached the Berlin Open quarter-finals before play was postponed because of rain.

Contesting his first grass court tournament of the season, Medvedev, a Wimbledon semi-finalist last year, lost out to Zhang as the world number 42 recovered from a 5-3 deficit in the decisive tie-break.

Zhang will meet Eubanks next after the Wimbledon quarter-finalist ended Bublik's title defence.

Also in Halle, former Wimbledon runner-up Matteo Berrettini, of Italy, won 7-6 (7-5) 6-2 against American Alex Michelsen.