The two sides meet in the Champions League on Wednesday.
The two sides meet in the second leg of their Champions League last 16 clashes on Wednesday, with the Catalan giants holding a 2-0 lead from the first leg.
As far as most are concerned that means the current holders are effectively through, with nobody giving the Gunners a chance of progressing at present.
Vermaelen though, has warned his teammates not to underestimate Arsene Wenger’s side as he remembers when they came close to beating Bayern Munich back in 2013.
“We will be the favourites, but I know it's not going to be easy against Arsenal. I think they gave us a tough time in London,” Vermaelen told the London Evening Standard.
“When I was there, we played a couple of times against Bayern Munich and we lost at home, but then we went to Bayern Munich and we had very good results.
“ We were close to going through. So you can never say Arsenal are out, because they will always come back.”
The bigger problem for Arsenal is that they are heading to the Nou Camp with confidence at its lowest in a long time.
Sunday’s FA Cup exit at the hands of Watford will not have gone any way to improving that either, with that competition having been their big hope of some silverware this season.
Still, 2-0 is not the end of the world and a miracle could see them get something against the team many are backing for the Champions League again.