After an appalling start which saw Arsenal lose four from the first seven league games, the Gunners finally found their consistency with nine wins from 10 matches to overhaul Tottenham and Newcastle.
However, Arsene Wenger's side were unable to produce a winning response to their shock home defeat by Wigan when held to a frustrating goalless draw by Chelsea.
While the Gunners remain very much still in the driving seat to go on and secure automatic qualification for the Champions League, Newcastle could move level on points should they win their match in hand, with Spurs' challenge perhaps dealt a fatal blow after a 1-0 loss at QPR.
Vermaelen accepts Arsenal could have given themselves some breathing space had opportunities been taken this past week.
"We didn't win the last two games, and they were really good chances to put ourselves into third place comfortably. At the moment we still have to fight for third place," said the Belgian centre-back.
"It will be a big effort for everybody to get that third place.
"It is not going to be easy, but that is because you play in England and it is not an easy league. Everybody can beat everybody.
"There are a lot of teams involved, ourselves, Tottenham, Chelsea and Newcastle. It is going to be tight, but it is going to be interesting.
"It is going to be hard to keep third place, but I am confident that we will."
Wenger laid down a challenge to his side ahead of their final three matches.
"We are still in the driving seat, no matter what happens, and it depends on the results we make now," the Arsenal manager said.
"We go to Stoke [next], to West Brom [on the final day], no easy places, and play Norwich at home.
"I think we need to win two out of the next three."