Goal has learned Brighton have now joined Aston Villa in the race for the goalkeeper, who played a starring role in Arsenal's FA Cup success last season having filled in for the injured Bernd Leno during the final weeks of the season.
Villa have so far tabled two offers for Martinez, but have yet to meet Arsenal's £20 million ($26m) asking price. Their second bid was close to that figure, but only after add-ons and bonuses were factored in.
Sources close to the Argentine keeper have confirmed to Goal that Brighton have now entered the running for the 28-year-old and have tabled an offer that exceeds that of the Midlands club, but it has not been accepted by the Gunners.
Villa are expected to return with another bid imminently, however, and remain confident that they will ultimately land Martinez, who will now not be involved on Saturday when Arsenal begin their new Premier League campaign at Fulham.
Mikel Arteta has taken the decision to withdraw the keeper from his squad amid such heightened transfer activity, with Martinez having now almost certainly played his final game for the club.
Speaking during his pre-match press conference on Friday, Arteta was quizzed on the future of his goalkeeper.
“I cannot stop speculation about all our players,” he said. “I don’t want to comment on any individuals at the moment without having the right answer to give.
“We have some really good players in many different positions and some of them are duplicated. Obviously clubs come to us and are interested in getting our players.
“It’s very difficult to promise our players game time or that they will be first choice. So it’s part of this period in the market. We try to manage the situation as well as we can.
“What the players expectations are and what we can achieve with them at the club. We are making decisions towards that.”
Martinez has been with Arsenal for more than a decade and his preference has always been to stay at the club, but having proved himself when standing in for the injured Leno at the end of last season he does not want to find himself back on the bench once again.
He has a contract until 2022 and the Gunners have been in talks to extend his deal, but Goal has learned the terms on offer are less than what Villa were willing to pay him, even before Brighton emerged as competition.
Villa have also given Martinez assurances over playing time should he make the move to Dean Smith's side, something that is key to Martinez's hopes of making himself Argentina number one in the near future.
The latest development over Martinez’s future means that Matt Macey will be on the bench for Arsenal against Fulham on Saturday, with Leno back in goal for the first time in the Premier League since he damaged his knee ligaments against Brighton last season.
Arsenal have long expected to lose one of their keepers this summer and have started looking for replacements.
Brentford keeper David Raya has been identified as a target, but the Bees are determined to keep hold of him as they look to challenge for promotion from the Championship once again.