The 35-year-old Australian last month announced he had opted not to take up the offer of another deal at the Riverside Stadium with his current contract due to expire at the end of the month, and will instead head for Craven Cottage.

That may have come as a disappointment to former team-mate Southgate, although he is confident in Ross Turnbull and Brad Jones that he has able deputies already in place.

But the manager was quick to pay tribute to a man who managed 446 senior appearances for the club in more than 11 years on Teesside, and picked up a Carling Cup winners' medal in 2004.

Southgate said: "We offered Mark a new contract because we felt his experience would be a help around the place for us.

"But all the time, I was very conscious that we have got two good young goalkeepers who need an opportunity.

"We are very grateful for what Mark did for this club. I had the good fortune to play with him and manage him, and from a manager's point of view, he was a very low-maintenance player.

"He is a very dedicated professional and a pleasure to work with, never a moment's trouble.

"He has been a fantastic servant to the club over the 10, 11 years he has been here.

"He played in some massive games for the club, cup finals, and was involved in us winning the first trophy and in our first European runs.

"I can't speak highly enough of him as a person and we wish him well with what is a new challenge."

Schwarzer joined Boro in a £1.5million switch from Bradford in February 1997.

Schwarzer was a key figure under Bryan Robson and successor Steve McClaren, and remained the number one choice when Southgate took over at the helm.

Perhaps his finest moment in a Boro shirt was a late penalty save from Robbie Fowler at Manchester City on the final day of the 2004-05 season to secure a 1-1 draw which earned the club its first ever – and to date, only – qualification for Europe via the league.