During the many years I spent refereeing football matches I learnt that it's ALWAYS the ref's fault when a team loses!
For example, one team wrote to both their own league committee, and to the County FA, to complain that they'd only lost a match because I'd accepted a bribe from the opposition. They'd been playing a cup game against a team 5 divisions above them and they'd lost 10- 1, but they still convinced themselves (enough to complain in writing!) that the only reason they'd been defeated was because their opponents had offered me a cup of coffee at half time ;-)
So I'm unsurprised when a team manager blames the ref for his side's poor performance. Indeed, I'm more surprised when it doesn't happen. (Alex Ferguson managed to get through a post-match interview with a BBC reporter today without accusing either the ref or the BBC of bias. That's got to be a first!)