Everton FC goalkeeper Tim Howard wants a clean sheet for USA tonight

"I believe I play in the best league in the world, so I am up against top quality strikers all the time.

"As a professional, if you don't test yourself against the best you won't know your own ability."

After an arduous season in the Premier League and the disappointment of an FA Cup final defeat, Howard acknowledged it was not easy to keep focused.

"We all face that challenge but if you want to be recognised as a full international or recognised as someone at the top of your game, then that's what is required," he said.

"There is a responsibility as an international player to get yourself fit and mentally prepared. At the end of a long season it is never easy but the best players do it without complaint."

Joseph Yobo, another Everton player to see his season extended by internationals, has ensured a frustrating summer so far.

Not selected for Nigeria's 3-0 defeat of Kenya last weekend, his journey to a Maltese training camp ahead of this weekend's World Cup qualifier against Tunisia has been delayed after he was one of three unable to secure a visa.

John Utaka and Israeli-based keeper Dele Aiyenugba were also denied visas and the Nigerian FA is frantically trying to resolve the problem so all three can join up with the squad.

The Blues, meanwhile, have confirmed over the weekend that Nuno Valente and Andy van der Meyde have been released at their end of their contracts and Segundo Castillo has returned to Red Star Belgrade at the end of his loan spell.

Youngsters John Irving, John Paul Kissock, Scott Spencer, Eunan O'Kane and Cory Sinnott have also been released by the Club.

Academy players Thomas McCready, Luke Powell, Michael Jensen and Daniel Redmond have also left.

Valente made just two appearances last season, while van der Meyde made a solitary contribution - admittedly a memorable one - the cross from which Dan Gosling scored the FA Cup derby matchwinner.