Bayern Munich striker Robert Lewandowski headlined the 23-man Poland squad for the World Cup in Russia, but an injury to defender Kamil Glik handed manager Adam Nawalka a last-minute worry.
The 30-year-old Glik, a stalwart of the Polish defence, injured a shoulder a little after the Fifa deadline for naming the final squad.
"During a training session, Kamil Glik suffered a ligament injury to his acromioclavicular joint,” the Polish football federation said in a statement.
The Monaco defender underwent preliminary tests in Poland and was due to fly to Nice for further treatment before a decision is taken on his rehabilition with a view to a return to full training, it added.
"He remains on our list. We await the results of the test,” federation spokesman Jakub Kwiatkowski said.
If Glik’s injury were to prove serious, he would be replaced by Stuttgart’s Marcin Kaminski, according to Nawalka.
Before heading to Russia on June 13, Poland have warm-ups against Chile in Poznan on June 8 and Lithuania in Warsaw four days later.
In Russia, Poland open their Group H campaign against Senegal in Moscow on June 19 before facing Colombia and Japan.
Poland World Cup squad
Goalkeepers (3): Bartosz Bialkowski (Ipswich Town/ENG), Lukasz Fabianski (Swansea/ENG), Wojciech Szczesny (Juventus/ITA)
Defenders (7): Jan Bednarek (Southampton/ENG), Bartosz Bereszynski (Sampdoria/ITA), Thiago Cionek (SPAL/ITA), Kamil Glik (Monaco/FRA), Lukasz Piszczek (Borussia Dortmund/GER), Artur Jedrzejczyk (Legia Warsaw), Michal Pazdan (Legia Warsaw)
Midfielders (9): Jakub Blaszczykowski (Wolfsburg/GER), Jacek Goralski (Ludogorets Razgrad/BUL), Kamil Grosicki (Hull/ENG), Grzegorz Krychowiak (West Bromwich Albion/ENG), Rafal Kurzawa (Gornik Zabrze), Karol Linetty (Sampdoria/ITA), Slawomir Peszko (Lechia Gdansk), Maciej Rybus (Lokomotiv Moscow/RUS), Piotr Zielinski (Napoli/ITA)
Forwards (4): Dawid Kownacki (Sampdoria/ITA), Robert Lewandowski (Bayern Munich/GER), Arkadiusz Milik (Napoli/ITA), Lukasz Teodorczyk (RSC Anderlecht/BEL)