The Blades top scorer, with 15 goals this season, has not played since going off injured at Reading last month.
But the 33-year-old will have his hamstring assessed on Friday, before the Blades travel down to Suffolk.
Blades boss Chris Wilder confirmed: “Leon is having a test before we travel. He's got to come through that.
“It's an important time of the season obviously. We don't want him to play one game and then lose him for the next 10.
“The one things about Leon is that, if he's ready, you always know he's going to stick his hand-up to play. James (Wilson, ankle) is the same. He was very close the other night.”
The Blades - ninth in the table, three points behind sixth-placed Middlesbrough - are looking to bounce back from Tuesday’s 3-0 defeat at Fulham.
“He's worked extremely hard, Leon, since coming off against Reading,” said Wilder. “All my players have been working hard, they all want to be involved. There's no picking and choosing games.
“We'll give him as much time as needed to get himself ready. The same as James. But I'm not going to stick him on the bench if he's got a big opportunity of missing a chunk of games.
“Hopefully the two or three days which have passed since our last game will give him that chance.”
Meanwhile, Blades wing-back Enda Stevens has been named in the Republic of Ireland squad for their friendly against Turkey later this month.