Speed, who played at Elland Road between 1988-1996, was found dead this morning.

"We are stunned to learn this news. The club expresses its deepest sadness," said a Leeds spokesman.

"Gary was very well thought-of throughout the game. He was a very likeable and popular man.

"It's very difficult find words to describe how we're all feeling right now."

The 42-year-old's playing days ended at Sheffield United, Speed joining the Bramall Lane club on January 1, 2008.

He enjoyed a role as first-team coach before being appointed as Kevin Blackwell's replacement as manager in August 2010.

However, his spell as boss was short-lived as he left south Yorkshire for the job of Wales manager in December 2010.

A statement from the League One club read: "Everybody at Sheffield United is extremely shocked and saddened to learn of the death of former player and manager Gary Speed.

"Thoughts are with Gary's family and friends at this distressing time."

Doncaster manager Dean Saunders, a former international team-mate of Speed, remarked on his dedication to his craft as a player.

"He was so fit - he was one of those players who would stay behind all day in training. I can't believe what's happened," Saunders told BBC Radio Five Live.

Asked if the Swansea game against Aston Villa should be postponed in view of the shocking news, Saunders added: "I just feel for his wife and his dad, I feel sorry for them more than the football."

Newcastle defender Steven Taylor, who came into the first team at St James' Park when Speed was the side's senior professional, expressed his gratitude for the help the midfielder gave him at the club.

"It is a sad, sad day. I played with him when I came through the ranks," Taylor told Radio Five Live.

"He helped me through, he was an absolute machine - the best professional in football.

"He had that aura about him. He always had time for the young lads and helped them feel good about themselves."

Wales are in the same group as Scotland in qualifying Group A for the 2014 World Cup and Scottish Football Association chief executive Stewart Regan was left shocked by the news having met Speed just days ago.

"I am speechless at the news of Gary Speed's death," Regan said.

"Craig Levein (Scotland boss) and I had lunch with him on Wednesday in Brussels. He was a talented young manager. So sad."