Arsène Wenger has conceded defeat in his fight to keep Cesc Fábregas and Samir Nasri at Arsenal and he has told the club's chief executive, Ivan Gazidis, to finalise their transfers to Barcelona and Manchester City as quickly as possible so that he can begin to pick up the pieces from two destabilising sagas.

The manager hopes to push through a deal for the Valencia winger Juan Mata and he has opened talks with Shakhtar Donetsk over the possibility of taking the attacking midfielder Jadson to the Emirates Stadium. He also has an interest in Marseille's Mathieu Valbuena and Lille's Eden Hazard.

Wenger has long realised, in private, that it would be extremely difficult to keep Fábregas from Barcelona's clutches for the third summer in succession, despite him being under contract at Arsenal until 2015, and it has been a case of attempting to extract the best possible fee from the European champions. The parties are finally set to announce agreement at €40m (£35m), with Arsenal having pushed successfully for the full sum up front.

Wenger confirmed that the transfer was finally afoot when he was asked whether the captain's future would be determined by the start of the Premier League season – Arsenal kick-off at Newcastle United on Saturday. "That is completely the truth," Wenger said. "We hope it will be sorted out very quickly one way or the other. We'll know very quickly."

Nasri's departure, though, feels a little more shocking, despite the fact that he has entered the final 12 months of his contract. Wenger was supremely confident in February that the midfielder would agree to fresh terms, which would have made him one of the highest paid players in the club's history, only for a stand-off to ensue.

Four weeks ago Wenger categorically ruled out Nasri's sale, stating that he would rather lose him as a Bosman free agent and write off a £20m-plus fee in order to keep him for one more season. Yet Nasri's head has been turned by the riches on offer at City, together with the prospect of trophies, which he feels is greater than at Arsenal and, from being relaxed about whether he stayed or went, his determination to depart has hardened.

There remains a difference between City and Arsenal in terms of Nasri's valuation but it is expected to be ironed out and the transfer completed before City entertain Swansea City on Monday night. Arsenal expect to bank £25m from the deal while Nasri could earn as much as £180,000 a week at his new employers.

The writing looked on the wall for Nasri's Arsenal career when he did not travel to Lisbon for last Saturday's friendly against Benfica, with Wenger citing a "muscular injury", only for him to fly to Montpellier on Monday and declare himself available for France's game against Chile on Wednesday. He started and played for 65 minutes.

"The Nasri situation is stable," Wenger said, which felt like an odd choice of word. "Again it is very difficult to speak about possible transfers but we are in a situation where we have to make decisions one way or the other. Ideally you want it to be sorted out before the season starts."

At the beginning of the tour of east Asia Wenger appeared to put reputations on the line when he declared Arsenal could not be considered a "big club" if they sold Nasri and Fábregas this summer – "because a big club holds on to its big players and gives a message to all the other big clubs that they cannot come in and take them away from you," he said.

Those words have a haunting quality as Wenger begins the salvage operation. Mata, the 23-year-old Spain winger, who can also play as a No10, has been tracked by Arsenal for some weeks and Wenger hopes the expiry of his €25m buy-out clause does not mean Valencia, who want to keep him, price him out of a move. With Mata keen to join, that is not expected to happen.

Jadson is a Brazil international, who played at the Copa América, but he might encounter problems in securing a UK work permit, having failed to appear in the requisite number of matches for his country over the past two years. He played for Shakhtar against Arsenal in the Champions League last season. Wenger, who is set to name Robin van Persie as the club's new captain, will be without Jack Wilshere at Newcastle because of an ankle injury.