We'll be fine as long as we work on our issues. Lucho is the most important person in the team right now, without him doing his part, it doesn't matter who we buy/bought. Things have to change beyond the transfers we make/made. Things like better stamina, more speed, greater workrate, no more lapses of concentration resulting in cheap goals being conceded, better tactical awareness and so on. Lucho has his work cut out for him and he really needs to show some qualities outside his bright blaugrana past.
About Vermaelen, he is not a bad player. He's not the best CB out there, that's certain, but in the right system with the right tactic and with the right support, he can deliver. So can Mathieu. They won't ever carry the team on their shoulders, but they won't dissapoint if the atmosphere surrounding the team is the right one.