The two were once close when they worked together at Barcelona, but they later fell out in spectacular style during the Portuguese's time as coach of Real Madrid in 2011.
A rivalry renewed. With Pep Guardiola now in charge at Manchester City, Jose Mourinho installed at Manchester United and the two teams flying high in the Premier League, one of football's famous feuds is ready for another chapter.
Guardiola and Mourinho worked together for four years at Barcelona. The Catalan was a midfield linchpin back then, the Portuguese an assistant to Bobby Robson and later Louis van Gaal.