The Dutch striker went for Raul Bravo after becoming incensed by a challenge from the defender.
Real stars Robinho and Roberto Carlos had to step in to restrain Van Nistelrooy as he squared up to ex-Leeds ace Bravo on Monday.
Boss Fabio Capello also told the hitman, 30, to calm down.
Van Nistelrooy was off-loaded by Alex Ferguson after the Manchester United chief became incensed with the forward’s poor attitude.
Van Nistelrooy also fell out with Dutch coach Marco van Basten — and he has left out the Madrid star from his squad to face England on November 15 in Amsterdam.
This latest incident casts another shadow over the Bernabeu where Real host Steaua Bucharest in the Champions League tonight.
It was just a matter of time