Niwa fell to a 9-11, 7-11, 11-6, 8-11, 11-9, 10-12 defeat at the hands of his opponent, who went on to lose his second-round encounter against Czech Republic’s Tomas Konecny 4-3.

Zhmudenko’s shock victory against Niwa overshadowed the impressive performances of Brazil’s Cazuo Matsumoto and Slovakia’s Bai He.

Matsumoto beat Japan’s Yuya Oshima, the number eight seed, 11-6, 11-6, 11-9, 7-11, 11-8 before going on to overcome Slovakia’s Wang Yang in six games.

Bai was in equally good form as he defeated Portugal’s João Monteiro, the number 12 seed, 11-7, 11-6, 5-11, 11-8, 11-9 and followed that up by outdoing Sweden’s Jon Persson in seven games.

Czech Republic’s Lubomir Jancarik was another surprise pacakage, beating the host nation's number 15 seed Wang Zengyi 11-8, 11-7, 15-13, 7-11, 11-6 before getting the better of Sweden’s Jens Lundqvist in five games.

There were no scares, though, for top seed Dimitrij Ovtcharov of Germany as he beat Poland’s Marek Badowski and then Hungary’s Adam Pattantyus, both in straight games.

Japan's Jun Mizutani, the number two seed, beat Ukraine’s Yevhen Pryshchepa 11-4, 12-10, 11-5, 11-6 before seeing off Russia’s Grigory Vlasov in five games.

In the women’s singles, there was an unexpected loss for number two seed Ai Fukuhara against fellow Japanese Hina Hayata.

Fukuhara beat Canada's Zhang Mo 11-7, 11-3, 11-5, 11-6 in the first round but was found wanting against her compatriot and found herself on the wrong end of a 4-1 scoreline. 

Spain’s Maria Xiao defied expectations to beat number 22 seed Ivan Ivancan of Germany 11-7, 8-11, 13-11, 12-10, 11-5, but came unstuck against The Netherlands’ Li Jie, who beat her in five games.

Japan’s Kasumi Ishikawa, the top seed, beat Slovakia’s Eva Odorova 10-12, 12-10, 15-13, 11-9, 11-8 and Singapore’s Jeng Zian in straight games.

Action in Warsaw is set to continue tomorrow.