After a mutually agreed fee, Mat Ryan, Brighton's goalkeeper is on the verge of signing for Real Sociedad.Ryan has signed the principle agreement on personal terms and will be undergoing a medical in this week's final year of his Brighton contract.Sky Sports News reported that Arsenal and clubs in France and Spain were interested in the Arsenal player, who was on loan at Emirates last season. He played three games during this period.The Scottish Premiership runners up Celtic are also looking at Ryan's move, with Ange Postecoglou, the new manager, keen to continue working with the Australia 'keeper after their time with the national team.Ryan was Postecoglou's No 1 choice for the Socceroos in the 2014 World Cup as well as their 2015 Asian Cup victory.Ryan wants to be the first-choice goalkeeper at his next club, and Sociedad in La Liga proved crucial.Sky Sports has the summer transfer window.Follow all the latest news and rumours about transfer in our Transfer Centre blog on Sky Sports' digital platforms. You can also keep track of all developments on Sky Sports News.