The Algerian didn't show up for training for more than a week after a deadline day move to Manchester City fell through.
He has since returned and scored his first goal since the debacle against Bournemouth last weekend.
"I think around the first game against Everton it was strange atmosphere around the team and it was a difficult moment," said Puel.
"We didn't have the good feeling or concentration about this game. It was a mistake, a difficult mistake in the game. Perhaps there was something around this game."