Why did things go sour for Northampton?

They lost against London Irish yesterday 25 - 23 but their sorry tale started when Matfield came from the bench - where he should have remained.   Came on first scrum collapsed no doubt due to poor support by the denuded tight 5.  Next line-out taken and Matfield went off-side when he tried to make a tackle from an off-side position - another penalty inevitable.
From being just outside their own 22 - they ended up being deep in the Northampton 22.
After that Northampton really went to pieces.  When the Irish ultimately ended up with a penalty inside the Northampton 22 - a series of deliberate illegal plays by the Northampton forwards ended up in a scrum.   The scrum was collapsed illegally and a penalty try under the posts was the result - the first win this season by London Irish.  
Where did things go sour for Northampt on?   On top of the list was Matfield - he is a serious handicap for any team he plays for.

Watched the game on TV......all I can add is that old Greybeard is way over the hill.
It is time for him to retire once again and hopefully forever.
Man some guys just don't get it.............

 He single handedly destroyed out tight five. Biggest disaster ever to play for SA!If only Dr Mozzzzz would wise up! I think he would still sele ct wee matfiled as his number 1 lock. Hahahahahahahahaha