Mari is available for selection for Thursday's Europa League clash against Olympiakos.
"Well, I watched the game but I could not be there for a personal reason. But, I was very glad that those two were there to support him," Arteta told a press conference.
"When he joined the club he hadn't played for a long time and he had a little niggle as well well when he joined us, but his attitude and commitment has been really, really good and highly surprising.
"He did really well the other day and hopefully we can start to use him soon."