Athletic would probably look for us to pay the release clause for Martinez and if they considered it a hostile approach (i.e. you can either pay the release and it be accepted by the club or they can still look at it as them not wanting to sell) we'd have to pay tax on top of that. Aguero's...
As an athlete, he's got slower, worse acceleration, lesser ability to make quick turns, etc. It's pretty obvious. He's a much better shooter and passer than back in the day but far less explosive.