The 21-year old Australian goalkeeper has made four impressive league appearances for the Belgian side since arriving from Central Coast Mariners in the off-season and the Brugge coaching staff feel he should be next in line for the Socceroos mantle.
"We are delighted by the way Mat has been progressing and I would say he is definitely ready for the next level of international football," he said.
"Obviously we wouldn't want to lose him for long journeys around the world but we have international players from other countries in our squad and you accept that and want to see them excel. I know Mat would love to represent his country."
Gretarsson also reserved more praise for Ryan in regards to his personality and overall ability.
"Mat has been looking better with every game and has been one of our most impressive players so far this season," he added.
"He's also integrated well with the squad and is a great character and a fantastic guy. He is always positive and very professional.
"He is explosive in his game and has made some great saves and is amazing on the ball with both feet he's like our eleventh on-field player at times and that's very important in the modern game."