Martin scored the only goal of the game in Man Utd's pre-season friendly against Orlando Pirates last month. He impressed last season in his loan-spell at the Lane just like fellow winger David Cotterill who has recently signed a three-year deal with the Blades.
"We already have the likes of Quinny and Armstrong who can play wide and lock things up to balance things out in that way but we might need someone who can provide something different on occasions, "said Blackwell.
"There is a possibility that we might still be able to do something with Lee and have asked Sir Alex to keep us informed.
"Lee has said he would like to come back because he enjoyed his time here - as did the other lads who came on loan last season - which is a good mark for this club."
Martin made 6 appearances in the last campaign in his three-month loan spell. He provided the assist in one of the most bizarre goals in FA Cup history. His outside of the foot cross met a gathered sky blue and white balloons which could steer the ball in track for Luton Shelton (now of Valerenga) who could slot past Joe Hart in the Man City net.