The former Gunners skipper is on his way to Manchester United to finalise the formalities of a £24million switch to Old Trafford, having earlier in the summer announced he would not be signing a new deal.
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.
Belgian defender Vermaelen is now likely to inherit the captain's armband, and insists everyone must put the disappointment of losing Van Persie to one side as they prepare for Saturday's kick-off against Sunderland at Emirates Stadium.
"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," Vermaelen told Sky Sports News.
"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."
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."
There could yet be more departures from Arsenal before the end of transfer window, with Barcelona said to be close to agreeing a £15million deal for Cameroon midfielder Alex Song, while Andrey Arshavin and Denmark forward Nicklas Bendtner could also move on.
Wenger, though, is also likely to look to use some of the extra cash generated to finalise his team, with long-time target Yann M'Vila still on the radar, as Rennes hold out for a £17m fee, along with Real Madrid Turkish midfielder Nuri Sahin.
Whatever happens over the next couple of weeks, if Arsenal are to avoid another late scramble for Champions League qualification and keep themselves on the fringes of the title battle, then they cannot afford another appalling opening spell like last season - which included an 8-2 humiliation at Old Trafford.
Defender Laurent Koscielny told Arsenal Player: "We saw last year that we had some difficulties at the start of the season, but afterwards you saw the real team.
"You need to work together, win together and help team-mates, and if [the start to] the season is good we can do something in the league.
"If we start well, we can get into the race for the title."
Alex Oxlade-Chamberlain (ankle) and Theo Walcott (thigh) will be assessed after both pulled out of England's game against Italy in Berne with injuries.