Ipswich goalkeeper Kelvin Davis was named as the number one keeper for the division but Sullivan was expected to be close in a voting system that sees all Championship players select their best XI.
Blackwell said in the Yorkshire Evening Post: "Sully can't have been far away. For me he would be in there, but he's my goalkeeper so I suppose I'm bound to say that. Sully has been magnificent for me this season and he couldn't have given any more.
"But if I had to go for someone other than Sully, it had to be Kelvin Davis. If he hadn't played as well as he has for Ipswich then they probably wouldn't be where they are now. If it had been anyone other than Davis, though, you could have knocked me over because Sully had to be up there."
No Leeds players made the side for a select XI that is dominated by promotion-chasing teams.
PFA Coca-Cola Championship team of the year:
Kelvin Davis (Ipswich), Graham Alexander (Preston), Tom Huddlestone (Derby), Gary Breen (Sunderland) , George McCartney (Sunderland), Jimmy Bullard (Wigan), Steve Sidwell (Reading), Julio Arca (Sunderland), Inigo Idiakez (Derby), Nathan Ellington (Wigan), Jason Roberts (Wigan).