The 27-year-old goalkeeper was on Sunday night included in the England squad for the World Cup qualifiers against Kazakhstan and Belarus just hours after a handling error had gifted Bolton the opening goal in a game the visitors went on to win 3-1.

However, Zola refused to slate his number one, instead reflecting on a "bad day" at the office for the ex-Norwich stopper, whom he backed to return stronger from the experience.

"Robert Green is a great goalkeeper," declared the Hammers boss, who took over from Alan Curbishley last month. "He has all my trust, all of the team's trust. Everyone believes in him.

"It has been a bad day, but I am sure next game he is going to save two penalties - football is like that.

"The important thing is that you are always confident in what we are doing, because they are the right things to do for us."

Before the home side had time to recover from Kevin Davies' gifted opener after 30 minutes, Green then could only parry a low shot which Gary Cahill bundled in from close range.

Although the Hammers got a lifeline through Carlton Cole on the hour, substitute Matt Taylor made sure of a first away win of the season for Bolton with a 30-yard free-kick four minutes from time.

The result was a reality check for West Ham, who had been carried on the wave of euphoria which followed the appointment of the Italian as Curbishley's successor and back-to-back league wins - another of which would have, albeit briefly, put the east London club on top of the table.

"Everybody knew that it would not be so simple," said Zola, beaten for the first time as Hammers boss in the Carling Cup at Watford a fortnight ago.

"The players need to improve certain things, you need to improve the mentality.

"We have to improve and believe that it won't be like this every time.

"Sometimes games like this can help you make one step back in order to make two steps forwards. I hope it will be like that."

Bolton boss Gary Megson felt his side were never really under any threat, but is aware more similar performances will be needed to steer clear of another scrap for survival.

He said: "We wanted to make ourselves solid, and knew West Ham would have a lot of possession - but most of that was going square or backwards."

Megson, though, stressed: "The football club have not won away games on a consistent basis.

"That is something like only our fifth win in the last 22 months.

"If you are doing that, it is going to cause you massive problems because then you have to be successful at home.

"We just managed to stay up last year, yet our home record was only six points different from when we had qualified for Europe.

"Our away record has been shocking and it is something we need to improve on."