Pavel Vrba refused to make excuses for his Czech Republic side after they were beaten 1-0 at home by Scotland on Wednesday.
Czech Republic also lost their previous match 3-1 in Poland in November and in response Vrba handed debuts to Sparta Prague midfielder Martin Frydek and Sloval Liberec goalkeeper Tomas Koubek - the latter standing in for the injured Petr Cech.
However, Ikechi Anya's 10th-minute goal was enough for Scotland to claim the win in Prague.
It may have been another disappointing evening for Vrba's men, but he is unperturbed by the defeat despite Euro 2016 fast approaching.
"I'm not worried, because we are in time to keep trying variations and new players have their chance," Vrba told CT Sport.
"Of course we know that we have fans disappointed because we did not win.
"In the first half we were a bit unlucky when we have a single event opponent conceded, while we had several promising situations, of which unfortunately we could not score.
"It was obvious that we were not long, but I do not want to make excuses, we lost and it is crucial."
Czech Republic won their Euro 2016 qualifying group, beating Iceland, Turkey and Netherlands to top spot, and will face Spain, Croatia and Turkey at the finals in France.