"It will be a similar test to the one at Ipswich, although they will be slightly more direct and physical, although they still play attractive football at the right times."
Blackwell who spent some of his time at Home Park says he has nothing but fond memories but their will be no sentiment on Saturday.
"I played in the play-off final at Wembley and it was a great season for the club. I also helped to put in place the youth system and cut my way into management.
"The fans were always great and i built great rapport with them, although i have a decent record as a manager there so hopefully that can continue for the Blades."
There will be a live match thread of the game on Blades Mad starting at 2:00pm.