Poland could be without Kamil Glik at the World Cup after the defender injured himself within hours of being included in Adam Nawalka's 23-man squad.
The Monaco defender hurt his shoulder while reportedly attempting a bicycle kick in a hybrid game of football-volleyball in training on Monday.
The 30-year-old had already been included in the list of players Nawalka submitted to FIFA and will undergo assessment in Nice on Tuesday.
Stuttgart defender Marcin Kaminski, one of 12 cut from the 35-player preliminary squad, will remain on stand-by until the extent of Glik's injury is known.
While the absence of the former Torino man would come as a major blow, Poland are able to call on star striker Robert Lewandowski for their first World Cup appearance since 2006.
Juventus goalkeeper Wojciech Szczesny and Napoli pair Arkadiusz Milik and Piotr Zielinski are the other headline acts, while Southampton defender Jan Bednarek looms as an alternative to Glik.
Drawn in Group H, Poland first face Senegal on June 19 before further clashes with Colombia on June 24 and Japan on June 28.
Poland's final 23-man World Cup squad in full:
Bartosz Bialkowski (Ipswich), Lukasz Fabianski (Swansea City), Wojciech Szczesny (Juventus), Jan Bednarek (Southampton), Bartosz Bereszynski (Sampdoria), Thiago Cionek (SPAL), Kamil Glik (Monaco), Artur Jedrzejczyk (Legia Warsaw), Michal Pazdan (Legia Warsaw), Lukasz Piszczek (Borussia Dortmund), Jakub Blaszczykowski (Wolfsburg), Jacek Goralski (Ludogorets), Kamil Grosicki (Hull City), Grzegorz Krychowiak (West Brom), Rafal Kurzawa (Gornik Zabrze), Karol Linetty (Sampdoria), Slawomir Peszko (Lechia Gdansk), Maciej Rybus (Lokomotiv Moscow), Piotr Zielinski (Napoli); Dawid Kownacki (Sampdoria), Robert Lewandowski (Bayern Munich), Arkadiusz Milik (Napoli), Lukasz Teodorczyk (Anderlecht).