"We did not defend well", said Cuper. "If those responsible are not happy with what I've done, I'll be the first to leave, there's no doubt about that".
However, the Russians raced into a three-goal lead, to take the tie away from the Egyptians.
There appeared little danger when Roman Zobnin's off-target shot dribbled towards goal, but under pressure from Dzyuba, Fathy threw an outstretched right leg towards the ball and turned it into his own net.
"The team has always defended well".
This was the case ahead of the opening fixture against Uruguay as well; Cuper confirmed Salah's fitness beforehand, but evidently did not pass the fitness test and thus didn't play a minute against the South Americans.
"I don't think it was a lack of concentration". Egypt is still without a victory in six World Cup matches.
Artem Dzyuba, scorer of the wonderfully-taken third against Egypt and an inspirational presence throughout, is a controversial firebrand of a centre-forward who would nearly certainly not have been involved here if Aleksandr Kokorin had not ruptured his cruciate ligament in March.
The North Africans came into their second group game, on the back of a 1-0 loss to Uruguay and were hoping to record points on the table, especially with the return of talisman Mohammed Salah.More news: Alonso wins Le Mans to edge closer to Triple Crown
For much of the 90 minutes at the St. Petersburg Stadium, the 26-year-old Egyptian tried to find space for himself, with his teammates unable or incapable to provide him with the kind of service he receives at Liverpool. "But that's how matches work".
GW: Seriously, I mean I think Salah will stay at Liverpool and I think that's the right choice, but you know, he was just such an unbelievable player all season long.
On show here was not the Salah that had tormented Roma and Manchester City, or scored 32 goals in the Premier League and 10 to power Liverpool to the Champions League final. "We weren't decisive enough".
The men in red have scored eight times in their first two matches after also beating Saudi Arabia 5-0 in the opening game in Moscow last Thursday.
"The national squad is above any individual, including myself", Cuper said.
"This morning, Zhirkov agreed to participate because for a few days he had been hurt, his ankle and foot, but we knew what to do against him [Salah] and we managed to fulfil that".
But by then, Russian Federation were already three up and this game was as good as gone.