Diego Herrera claims Real Madrid have already lodged a bid - reported to be £18million-plus - with the Latics but that there are other interested parties.

Manchester United are the other club regularly linked with the Ecuador international, who was signed initially on loan by former Wigan manager Paul Jewell in August 2006 from Villarreal before current boss Steve Bruce made the £2million deal permanent in January last year.

Bruce has resigned himself to the fact the 23-year-old will leave in the summer but, as he did when Tottenham came in for midfielder Wilson Palacios in January, the Latics boss is determined to hold out for the best price.

Herrera said with interest in his client from some of Europe's biggest clubs it was now difficult for him to stay at Wigan.

"Wigan revealed last week that there has been an offer from Real Madrid but they haven't told me any details about it," Herrera told PA Sport.

"I don't know how much the offer is and I haven't yet talked to anyone from Madrid about details of a contract so I don't know how long they would want him for.

"Wigan have not confirmed anything to me about Manchester United's interest.

"I know there are other clubs interested but as far as I know there's nothing official.

"I have yet to sit down with Antonio and see what he wants. We've not yet talked about which club he would prefer.

"Honestly I think it's really difficult that he remains at Wigan. I would anticipate that he leaves this summer.

"We have to see what will happen in the next few weeks. We're not in any rush."

Valencia and his agent may not be in any hurry to seal a deal but Bruce will want any transfer completed as soon as possible.

Speculation about Valencia's future has affected the winger's performances in the second half of the season and the Wigan boss is determined to avoid a strung-out transfer saga.

The sooner he can offload the player the sooner he can start finding replacements and reinforcements for his squad, who were close to challenging for Europe this season until results tailed off in the final two months.

With Amr Zaki's loan from Egyptian club Zamalek not being made permanent and Mido's temporary spell from Middlesbrough due to end next week Bruce has made signing a striker a priority.

He has been linked with Christian Benitez, another Ecuador international, but the £7million asking price from Mexican club Santos Laguna may prove prohibitive.

Even if he does make a huge profit on Valencia Bruce will not pay over the odds, especially as he will have other areas to strengthen.

Bruce is expected to bring in Honduras midfielder Hendry Thomas when the transfer window reopens, having failed 12 months ago because of work permit rules.

But Paul Scharner, comfortable in defence or midfield, could be heading out of the club after reportedly saying he had aspirations to play at a higher level.

"I feel this summer is the time for me to make the next step in my career," the 29-year-old told Austrian TV.

"I'm looking towards getting a regular starting place in the Austria national side.

"My absolute aim would be to play in the Champions League."