Ugo Ehiogu, the former England defender, is in hospital after collapsing at Tottenham Hotspur's training centre on Thursday.
The 44-year-old, who works as Tottenham's Under-23s head coach, received treatment from the club's medical staff before being transferred to hospital by ambulance.
A statement by the north London club posted to Twitter read: “We can confirm that Ugo Ehiogu is currently in hospital after collapsing at our training centre earlier today.
“Our Under-23s coach received immediate treatment on site from our medical staff before being transferred to hospital by ambulance.
“Everyone at the club sends their best wishes to Ugo and his family. We shall continue to provide updates when we have further information.”
Ehiogu took charge of Tottenham's Under-23s in July 2014 after working at the club's academy on a part-time basis.
The Homerton-born defender started his playing career at West Bromwich Albion before moving to Aston Villa in 1991.
Villa, who Ehiogu represented on a total of 308 occasions, sent a message of support to their former defender, tweeting: “Get well soon, @UgoEhiogu! Everyone at #AVFC wishing you a speedy recovery.”
Ehiogu made his international debut in May 1996, two weeks prior to the start of that summer's European Championships, but he failed to make the cut for Terry Venables' final tournament squad.
He won three further caps for his country, scoring his only international goal in a 3-0 friendly win against Spain in February 2001.
Ehiogu joined Middlesbrough in November 2000 for a then-club record fee of £8million. He made 153 appearances for the Teesside club, before spells with Rangers, Sheffield United and non-league side Wembley.