Tristan struggled with his fitness when he arrived at Upton Park six months ago but he has adjusted to the pace of the Barclays Premier League and has two goals in his last three games.

With Carlton Cole still not back from a groin injury, 33-year-old Tristan is likely to lead the attack against Liverpool tonight.

"The problem with Diego was the physical condition," Zola said. "When he first came here in November he wasn't as good as now physically.

"Other than that Diego Tristan has got everything and he can be a top striker in Europe easily.

"Don't forget he has been a national player for Spain and has been top scorer in that country for many years. He just lost a little bit of it in the last few years but he is getting back very, very quickly and in the last few games he has been outstanding."

Zola feels Tristan has put himself in line to earn a new contract and stay at the club beyond the end of the season.

"Obviously he has put himself in a strong position," Zola said. "I think he is playing for his future, but more than that I would say he is playing because he is enjoying it.

"I haven't spoken to him but I believe he wants to stay."

Meanwhile, the Hammers face a hearing two days after the Premier League season finishes to see if they will be allowed a UEFA licence for next season.

A panel appointed by an independent specialist dispute resolution body will decide on May 26 whether the club will be given the licence they need to play in the Europa League, should they finish seventh in the table.

The licence can only be granted when certain financial documents are submitted - but the likely change of ownership at Upton Park means West Ham have not been able to do that.

The Hammers are confident they will be in a position to supply all the required information ahead of the deadline.

A statement from West Ham read: "Due to a number of factors, principally relating to a possible change of ownership of West Ham United, the club has not been able to submit certain financial information, but expects to be in a position to do so by May 26."