The Hammers fended off interest in the 30-year-old during the transfer window from a number of rivals in the Barclays Premier League.

Zola and the club's new owners, David Sullivan and David Gold, see retaining the likes of Upson and goalkeeper Robert Green as a major coup for the club.

And the Italian, whose side take on Burnley in the league tomorrow, believes Upson can secure his place on the plane to South Africa with some excellent performances for West Ham.

Zola said: "I think he has been playing very well. He didn't perform as well as he could at the start but now he's one of the best players I've had.

"His mental strength is getting better and better. I know he has two very good players in front of him [in the England team], it depends on the condition of those players.

"He knows the World Cup comes through the performances he has with West Ham."

Zola also saw his attacking options bolstered in January by the capture of three strikers.

South Africa striker Benni McCarthy joined from Blackburn along with Brazil international Ilan, who arrived on a free transfer from St Etienne.

Former Tottenham striker Mido also signed on loan from Middlesbrough on a contract reported to be around £1,000 per week.

The 26-year-old Egyptian has made no secret of his desire to play in the Premier League once more, and Zola has backed him to silence his critics.

Zola added: "Ilan has trained only twice but he looks a very good player. He is sharp, a skilful player.

"Mido and Benni - we know Benni - and Mido has been a surprise, he's working very hard and he wants to prove himself.

"He has started with a perfect attitude which is very important. He knows that everything he desires he will have to work hard for.

"I have been very pleased. He's had problems, but he is a player with great potential. With his quality he should be playing for a big team.

"If he wants to achieve it, he has a chance because this team will pick itself. I never bother too much about what the players earn, I judge them on the pitch.

"What they earn is a consequence of a good performance on the pitch."