Slovakia's manager admits that defence is already a concern for him ahead of the March Euro 2020 play-off against Ireland in Bratislava.
With some of his players on a winter break at their clubs, particularly in the domestic league, national team boss Pavel Hapal has been able to take a 30-strong squad to Turkey for a training camp.
The form at Newcastle United of Martin Dúbravka, voted Slovakia's player of the year for 2019, is a boost for Hapal and there has been one major transfer involving their squad, a record €27m move from Celta Vigo to Napoli for midfielder Stanislav Lobotka.
But inaction due to injury or loss of form for defenders like Dávid Hancko (Sparta Prague) and Peter Pekarík (Hertha Berlin) is a worry.
"I am not happy that some players do not play, such as Hancko. And since we have a bit of trouble in positions like the left and right side of defence, it bothers me," Hapal said.
"I need the players to fit and be playing, so that they are ready for March."
While Darren Randolph (Middlesbrough to West Ham) is the only member of Mick McCarthy's senior squad to make a move to date in this transfer window, Slovakia have been encouraged by a couple of transfers involving their players.
That fee of €27m for Lobotka's move to Napoli is a record for a Slovakian player, though that will be broken if the €60m-rated defender Milan Skriniar leaves Inter Milan for Spain this month.
Attacking midfileder Ondrej Duda has also moved to get more game time, leaving Hertha Berlin to join Norwich City on loan.
"I am delighted that Stan Lobotka has moved into a better club," said coach Hapal.
Ireland play Slovakia in Bratislava on March 26.