His coaches at Ajax were Stefan Kovács and Rinus Michels, who designed the famous Dutch offside trap around him and Velibor Vasović.

In 1978, Blankenburg moved to Chicago Sting in the United States, before being loaned out for a few months to KSC Hasselt in Belgium.

However, in 1982 he moved to lower league teams Hummelsbütteler SV and Lüneburger SK, where he finally ended his career in 1985, aged 38.

Blankenburg was never selected for the West Germany national team, one of the reasons being that the outstanding Franz Beckenbauer fulfilled the role of libero there at the time.

Johan Cruijff asked him to play for the Netherlands in the 1974 World Cup but Blankenburg refused, he was still hoping for selection from his homeland.