One of the greatest-ever footballers, the 88-year-old is stable but in a serious condition.
The Argentina-born player won five successive European Cups with the Spanish giants, and was European Footballer of the Year twice.
The forward also enjoyed success with River Plate and Colombian side Millonarios.
Weeks after lifting the European Cup in 1967, Jock Stein's Lisbon Lions provided the opposition for Di Stefano's testimonial at The Bernabeu Stadium.
Celtic underlined their status as kings of the continent by winning.
Three years earlier, Jimmy McGrory had made an audacious bid to sign di Stefano for the Bhoys.