Former England and Aston Villa defender Ugo Ehiogu has died at the age of 44 after suffering a cardiac arrest at Tottenham's training centre on Thursday.
A Spurs statement said Ehiogu died in hospital in the early hours of Friday.
Ehiogu, who was Spurs' Under-23s coach, was capped four times by England.
"Words cannot express the shock and sadness that we all feel at the club," said Tottenham's head of coaching and development John McDermott.
"Ugo's immense presence will be irreplaceable."
Ehiogu made over 200 appearances for Aston Villa between 1991 and 2000 and then spent seven years at Middlesbrough.
He won the League Cup with Villa in 1994 and 1996, and also with Boro in 2004.
The centre-back also played for West Brom, Leeds, Rangers and Sheffield United, before retiring in 2009. He began coaching at Tottenham in 2014.
Ehiogu was a co-founder of music label Dirty Hit, which has British indie band The 1975 on its books.
He married his wife, Gemma, in 2005 and had two children - son Obi Jackson and daughter Jodie.
Villa will hold a minute's applause before their Championship match against Birmingham City on Sunday, with both sets of players to wear black armbands.
"I can't fathom he's no longer here," former Middlesbrough goalkeeper Mark Schwarzer, who won the League Cup with Ehiogu, told BBC Radio 5 live.
He added: "He was a tremendous person, a tremendous character, a dedicated footballer and dedicated to his family. He was a great guy to be around, so full of life and so enthusiastic.
"As a centre-back, I rate him right up there. He suffered from injuries throughout his career, but with more consistency he could have added to his England caps.
"He was very much a family man and it's such a shame to leave such a young family behind."
Former Aston Villa team-mate Andy Townsend told BBC Radio 5 live: "He was a defender every team would like to have at the back. It's a life that is so tragically cut short and so sad.
"He was on the training field with the academy boys and would have stayed active. I saw him recently and he was a picture of health, which is why this come as such a huge shock."