Ronald De Boer has admitted there's nothing quite like the rivalry that exists between Rangers and Celtic.
The Netherlands legend competed in quite a few Old Firm derbies during his four-year stint at Ibrox, winning the Premiership in 2003.
Games between Rangers and Celtic are known as some of the most hostile in the world of football, and De Boer, who also played for Barcelona, claims that even El Clasico is a family event in comparison to the 'extreme' scenes during a Glasgow derby.
He told Four Four Two: "Old Firm games were the most intense games I played in – you can’t compared it to El Clasico in that sense. In Spain, people see it more as a family day trip.
“It’s intense, but Rangers against Celtic is more extreme – you feel that the whole stadium is fanatically involved.
"The games were always very physical. I remember some tackles where I was thinking, ‘This can’t be possible – back in Holland we would have had three or four red cards already!’ The referees would just wave incidents away, or just give a free-kick at most."
Indeed, Old Firm derbies invariably throw up flash points in the form of dangerous tackles or red cards.
In September, Jordan Jones was sent off for Rangers after lunging in on Celtic loanee Moritz Bauer toward the end of a 2-0 victory for the Bhoys at Ibrox.
There are several more meetings this season and it could well decide where the Premiership title goes.
Celtic, going for nine titles in a row, level again with Rangers after Steven Gerrard's side slipped up this past weekend.
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