So Phil Senderos has officially left Arsenal – two seasons after he effectively did anyway.

There’s been a lot of goodwill on Twitter and across the blogs and that’s fair enough. Senderos was an uncomplicated player who gave his all, never moaned and represented the club very well indeed.

He was an up-and-down player though, with some commanding performances early in his career contrasting with plenty of wobblier ones at other points. Perhaps not surprising for a young player – one who is still only 25 years old now.

But I’m glad he’s gone.

Why? It’s got nothing to do with him at all. He’s a player who can and probably will still come good given the chance and a fair wind with injuries. Who knows, that may have happened at Arsenal in the past, but it’s not going to happen now. So he needed to go to reignite his own career, but nor is it a bad thing for Arsenal either. As a club, we need to properly address our defence, and we won’t do that by looking backwards.

Which is why there’s no reason to despair at the prospect of Gallas, Silvestre and even Campbell’s departures either. All are past their best, and while Campbell is a special case – his desire was palpable and put others to shame at times last season – even in a best-case scenario he’d have been third choice in 2010-11.

Look at our defensive record over the last few seasons. We’ve conceded 8, 9, 13 and 9 goals more than the league winners since we moved to the Grove, a consistent deficit. We have not eradicated bad defending as a unit, nor have we eradicated individual lapses of concentration – so much so that we are now seen as defensive soft touches. We get targeted between the sticks and we get targeted at set pieces. Such targeting often works.

That’s got to change, and a clean sweep of the brush might not be such a bad thing.

There’s no point worrying that if all three depart, then we’ll only have Djourou and Vermaelen left. There’s no way Wenger would leave it that way.

Sure, there’s a risk that starting next season with a new keeper and two new centre backs might be unsettling for a while. But it’s a risk worth taking compared to another season of the same problems.

In the meantime, I hope Big Phil makes it big and proves Wenger wrong. Not many players have left and done that – but I can’t imagine many Arsenal fans would begrudge him a renaissance if he did.