The Argentine was a key part of the Gunners' FA Cup winning squad last year after being handed his chance in the side due to Bernd Leno's injury, but he spent several years as a second-choice goalkeeper in North London.
Arsenal's decision to let Martinez go raised eyebrows following his strong performances at Villa Park, but Arteta - who has seen Aaron Ramsdale establish himself as the club's number one - has insisted that the right call was made.
Speaking to reporters at a press conference, Arteta said: "We made decisions with the best possible interest of the club. But as well a big participant was Emi. He got to a point in his career where under me he started to play big games very well.
"It was urgent for him because he wanted to play so long. He's a great kid. I played with him I managed him. I can say that I'm happy for him."
Martinez shipped three goals to his former club in a 3-1 defeat at the Emirates on Friday night, including a Pierre-Emerick Aubameyang tap-in after he had initially saved the striker's penalty. body check tags ::