 Complete the following phrase:  After retiring from playing, Sabella became a coach and began a long association with fellow countryman and close friend Daniel Passarella, serving as his assistant manager during Passarellas spells managing Argentina, Italian club Parma, Uruguay, Mexican club Monterrey and Corinthians in Brazil. The duo finally returned to River Plate for whom they had both played before Sabella struck out on his own to become manager of Estudiantes in his own right, winning the Argentine Primera División Apertura championship and the 2009 Copa Libertadores. Sabella resigned from Estudiantes in February 2011 and was subsequently appointed as the coach of the Argentine national side, coaching them to the 2014 FIFA World Cup 