The 21-year-old left-sided player becomes the third new arrival at the DW Stadium in just over 24 hours.
"Patrick is a player with enormous potential," said Martinez.
"Technically he is very gifted, very comfortable in possession and physically, he uses his intensity to defend very effectively.
"He can play left-back or left wing-back and without a doubt he's got a phenomenal career ahead of him.
"We rate Patrick really highly and his professionalism and his personal attributes will be a huge asset to us this season.
"Like Tom Cleverley (on loan from Manchester United) last year he is a young player who is hungry to learn his trade and I feel both parties can benefit hugely from the move."