And the 22-year-old is quick to pour praise on Watson, a former England Under-21 keeper who was forced to quit with a knee injury at the age of 28.
Hart said: "Dave has been great to me. He's had a huge impact. He's absolutely 115 per cent behind you and he'd do anything for you.
"I'd like to think that I paid him the same respect as he has paid me. He's been great to work with and all three of the keepers here - myself, Maik Taylor and Colin Doyle - are improving.
"Dave does work us hard but it's not needless flogging and there's a lot of thought that goes into what he does.
"I give him a lot of grief but there's a lot of care that goes into it with the ultimate goal being to make people better goalkeepers. I thank him for a lot."
Blues boss Alex McLeish is full of praise for Hart who overcame a sticky spell during the early part of the season to help the Midlands' club earn a top 10 spot in the Premier League.
McLeish said: "Joe has been superb. Joe is his biggest critic and, in the early part of the season, he looked at goals he conceded and said 'I've not saved you points yet - but I will'.
"He has been true to his word and a good keeper is worth 10-12 points a season and Joe has certainly done that.
"He has certainly earned his high praise and involvement with the England squad and I think he has merited his call-up for tonight's game.
"It is down to whether Fabio Capello decides to give him a crack at it from the start."