Carson played in last night's England U-21s 2-0 victory against Wales at Ewood Park.
Blackwell told the Yorkshire Evening Post: "Scott Carson has been unbelievable in training and I think that has driven Sully (Neil Sullivan) on. He knows he has to play well to stay in front of Scott.
"I've had to fend off interest in Scott. He only turned 19 two weeks ago and he is an established member of the England Under-21 squad.
"It's frustrating for me that I can't play him at the level I want to. I know I'm the envy of Premier League clubs in the goalkeeping department. He's got the quality to follow Robbo and go all the way."