The Spaniard joined the Gunners from Malaga just before the January transfer deadline, and was pitched into action against Stoke less than 48 hours later.
"He joined us on the Thursday, trained on the Friday and then went straight into the side. I've been impressed with the way he has started here," Vermaelen told the official Arsenal matchday programme.
"He has done well, and you can see that he's a good player with plenty of quality. He's quick and solid, and plays for his national team - he's also a nice, relaxed guy to talk with. I think he will be a great signing for us.
"He's had a tough start with two typically 'English' games, completely the opposite to what he'll have faced in La Liga, but he's shown that he can cope and I have no doubt that he will do well in the Premier League."