"It's not necessarily the people within the club but just the level you are playing at and what you are playing for. I've always said that Michael Carrick was like a Rolls Royce. He needed to put his foot down and have to run to show what it could do - and I'd say the same with Gareth.
"At the moment he can walk into the Aston Villa team. He is guaranteed a place. At Liverpool there will be a massive amount of pressure next year. There will be more demands of him at Liverpool than there would be at Villa and he needs to go to reach that level."
Platt, who worked with Barry during his stint as England Under-21 coach, added: 'People can get disgruntled about things but it's just my opinion.
"Martin O'Neill knows more about the Gareth Barry situation than me. I've got nothing against Martin. He has done exceptionally well and he's just had a good season with Villa."