Rafa Benitez and Alex Ferguson did not exactly enjoy a particularly warm relationship while co-existing in England's northwest. Their relationship played out along the lines of many of Ferguson's counterparts: a reasonably warm relationship that cooled when said rival became competitive.
Their relationship hit a nadir in 2009, when Benitez' Liverpool went toe-to-toe with United for the title. In January, Benitez read his list of 'facts' leveled at 'Mr. Ferguson' at a press conference ahead of a game at Stoke, a moment made infamous by Liverpool's subsequent failure to win the game.
The net result was a feud: there was a bizarre farrago of Sam Allardyce accusing Benitez of disrespect with a hand gesture during Liverpool's shellacking of Blackburn, with Ferguson branding Benitez "disturbed".
The rivalry ended as many of them tended to: Ferguson had the last laugh by winning the league.
But despite their falling out, it turns out that it was Ferguson who first gave Benitez his introduction to English football as a manager, according to Benitez' former assistant Pako Ayesteran.
Ayesteran gave an interview to the Daily Mail to put himself in the shop window for a managerial gig in England, and revealed that Ferguson was very helpful to Benitez in the early stages of the latter's managerial career:
It's funny, but one of our first tastes of the Premier League was actually with Sir Alex Ferguson.
We were between jobs in 2000, so we went to visit Manchester United. Ferguson let Rafa and I watch his first-team training sessions with Roy Keane, Ryan Giggs, everyone in that great Treble team. At that time, it wasn't as normal to let foreign coaches come over to observe. It was very kind.
The pair then took over Valencia, and two La Liga titles and a Uefa Cup later, they pitched up at Liverpool and the rest is history.
It's an interesting interview, which you can read here.