Liverpool were strongly linked with a move for Heinze during the Summer, but stories developed about United boss Alex Ferguson, being unwilling to let the Argenitine join their rivals.
Martinez is a 19 year old central midfielder who has really impressed in La Liga in recent times. Both him and team mate Fernando Amorebieta were linked earlier in the month with a move to Anfield. Rafa Benitez is thought to have a scout tracking both players progress.
Madrid's Heinze would be likely to cost the club about £6 million and the pair of Bilbao players would be at an estimated cost of about £16 million.