The Belgian has been a revelation since his summer arrival from Ajax.
And Graham told TalkSport: "Outstanding. I think he's pure class. He reads the situation, he's probably just under six foot, got a lovely spring, fairly educated left boot - look at the goals he's scored. It's unbelievable, what a signing he's been.
"He's even more polished than I expected. I like the usual big, strong centre-halves and I still think Arsenal could do with one of those. Somebody at the back who's mentally and physically strong but Vermaelen is the whole package."