The former Gunners skipper is on his way to Manchester United to finalise the formalities of a ?24million switch to Old Trafford, and Belgian defender Vermaelen insists everyone must put the disappointment of losing Van Persie to one side as they prepare for Saturday's kick-off against Sunderland at the Emirates Stadium.
The defender, who is now likely to inherit the captain's armband from the Dutch striker, told Sky Sports News: "He was fantastic for us in the last year, scored lots of goals and I am disappointed he is going, but we have to focus on the next season with Arsenal."
He added: "We have to fight and I am confident we have a squad to win something. We start Saturday and this is all clear now, Robin is leaving and we have to move on."
Press Association Sport understands Arsenal were prepared to make their key striker, who last season bagged 30 Premier League goals, the highest paid player in the club's history, but reluctantly agreed to sanction his departure when it became clear Van Persie wanted to move.
Gunners boss Arsene Wenger insisted the club were left with "no choice" but to allow Van Persie to leave. However, he maintains the summer additions Olivier Giroud and Lukas Podolski will "offset" the loss to the squad, as will the arrival of Spain midfielder Santi Cazorla.
"It is never great to lose players of that quality, but he only had a year contract so we do not have a choice," said Wenger whilst working for French TV station TF1.
"We wanted to avoid that at all cost, but we weren't able to. Honestly, I'd have preferred to sell him abroad, to PSG, for example, over Manchester United.
"They have the advantage of having played against him and knowing his great class. He's truly an exceptional player in every sense of the word.
"We have already recruited since we bought (Olivier) Giroud and (Lukas) Podolski who originally were intended to offset the departure of Van Persie."
Source: PA
Source: PA