The Czech international has now conceded seven goals in games against Bolton and Liverpool– both at home – and will be under further scrutiny ahead of Saturday's FA Cup semi-final against Arsenal at Wembley.
Cech looked uncharacteristically vulnerable against Liverpool, but played down concerns about his form.
"Sometimes, you can't avoid making mistakes. It's an exception. It can happen," he said.
Cech was embarrassed in the 19th minute of Tuesday night's match when Liverpool left-back Fabio Aurelio swept an opportunistic free kick past him from wide on the right to open the scoring.
"I was concentrating too much on a possible cross and I'd already taken a step forward. After that, it was no longer possible to stop the shot," the 26-year-old admitted.
"I do everything to always be at 100 per cent, but sometimes it just doesn't happen," he added. "That was the case in the match against Liverpool."
Cech was keen to stress that the games prior to the matches against Liverpool and Bolton had been "without problems".
"My previous matches were good. Can that change after two matches?" he asked.
"But, on the other hand, it will be the decision of the coach (if I play). I cannot influence him," he added when asked about the possibility that he could lose his place to Chelsea's Portuguese reserve goalkeeper Hilario.
Hiddink admitted Cech is struggling for confidence but hinted that he would keep faith with the goalkeeper."He [Cech] is very intelligent and self-critical, and wasn't happy with his performance against Bolton [last Saturday]. Always, even when he has an almost perfect game.
"You could see he wasn't at full confidence. When it's a goalkeeper, it can have repercussions in goals. But he will stay a very good goalkeeper."
"Every person has this small period of not being in top form. It's not always a reason to replace someone."