Great Britain's place in next year's Davis Cup qualifiers remains uncertain after Wimbledon champions Julian Cash and Lloyd Glasspool were stunned in the doubles by Poland's Karol Drzewiecki and Jan Zielinski.
The world number one pairing, making their Davis Cup debuts together, could have given Britain an unassailable 3-0 lead in the tie in Gdynia but went down 3-6 6-3 7-6 (8-6) to the Polish duo.
The result means the onus will be on British number two Cameron Norrie to book his country's place in February's first round, with Britain's lead trimmed to 2-1 in the best-of-five tie.
Norrie takes on world number 484 Olaf Pieczkowski in Saturday's second rubber.
Britain require just one win on Saturday to take victory in the tie after Norrie and Arthur Fery, making his Davis Cup debut, both won their respective singles matches on Friday.
However, defeat in Poland would mean a February play-off which could result in relegation to World Group 2.