André Villas-Boas remains unrepentant over his criticism of the referee Chris Foy following Sunday's derby defeat to Queens Park Rangers and will defend his comments in correspondence with the Football Association this week.

The FA contacted Chelsea on Tuesday seeking an explanation for the manager's assertion that Foy and his two assistants lacked consistency in their approaches to the two sides at Loftus Road. Villas-Boas claimed the referee was "very poor", "card happy" and had "lost it" as he sent off Didier Drogba and José Bosingwa and booked seven other Chelsea players in the 1-0 defeat, with only two home players cautioned.

André Villas-Boas sought out Foy in the aftermath of a fractious game and admitted he had been "very aggressive" when confronting the official in the tunnel, a reaction the FA will now assess before determining whether any sanction – most likely a heavy fine but potentially a touchline ban – is required. Yet Villas-Boas, who has until Friday to respond to the FA, stands by his comments and reiterated them in the buildup to Wednesday evening's Carling Cup fourth-round tie at Everton

"I don't think I said anything I shouldn't have," said Villas-Boas, who has spoken to the referees' chief, Mike Riley, to discuss the matter. "I was cold, emotionally, and chose the right words, and I never doubted the referee's integrity. It is a game refereed by humans, so human mistakes will always be present. I am not questioning the referee's integrity but his decision-making in this game.

"The fact is that, at the moment, we are paying heavily in terms of major decisions. Maybe this is what the FA do not want to hear from me: phrases like, 'the referee has influenced heavily three of our games.' But [Foy] didn't show consistency. There was no coherence in the decisions he was making. I will stick to my words and reiterate that the same criteria were not applied to both teams.

"If you decide on one route, you have to stick to it for the rest of the game and I have full evidence that wasn't the case. He set the route by giving a soft penalty [against Chelsea] early in the game but then did not follow that route. That is why I am disappointed. Chris, in this particular game, was card happy and didn't show a pattern to what he's done in the past. What happened in this game was surprising given what he'd done before."

The FA has also charged Chelsea, who incurred a mandatory £25,000 fine for the number of bookings accrued, with failing to "ensure their players conducted themselves in an orderly fashion" after a handful surrounded Foy following Bosingwa's early dismissal. Chelsea opted not to appeal against that decision for fear that the full-back might end up having the suspension extended beyond the game at Everton.

They will also be without Drogba at Goodison Park, together with Ashley Cole – who was shown his fifth yellow card of the season on Sunday – and the cup-tied Raul Meireles. There are likely to be rare appearances for Ryan Bertrand and Josh McEachran, while Romelu Lukaku is likely to start up front. John Terry, who has had four bookings this season, is not expected to be involved, with Saturday's lunchtime match against Arsenal at Stamford Bridge in mind.

Villas-Boas had cited decisions that had gone against his team in visits to Stoke City and Manchester United but maintained he retains faith in the standard of refereeing in the Premier League. "Don't get me wrong, I'm not unhappy with the referees," he said. "It's just that it's been happening quite a lot for us. It's been a pattern in three games. But we have to do better, too. We expected to play better at QPR when we had 11 men but we were not good enough. So we take total responsibility for that."