The Foxes boss has conceded that he is not sure when the Republic of Ireland international will be ready for a return to competitive action
St Ledger has been sidelined since November 2013 after picking up a groin injury in a friendly international game for the Republic of Ireland against Poland.
The 29-year-old's recovery was then hindered when he received a further set-back with a knee complaint and he has since been to Germany to have the injury assessed and treated. However, the Foxes boss conceded that they have been "unable to resolve" the defender's knee issue and could not set a date for his recovery.
"I am not going to put any timescale on Sean because, at the moment, we don't really know how long he is going to be out," Pearson was quoted as saying by the Leicester Mercury.
"It is frustrating for the lad because he has had a difficult year coming through some frustrating setbacks for him. He has a knee problem that we have been unable to revolve so far.
Meanwhile, Kevin Foley has joined Blackpool on a one-month loan from Wolverhampton Wanderers.
The 29-year-old said that it was a "no-brainer" for him to join the Championship side, having played just seven times for Wolves this season and not featuring for the club since October 2013.
"It was a no-brainer to come and play football for a good side," Foley told the club's official website. "Barry [Ferguson] showed an interest, so I was more than happy to come up here.
"I heard about the interest a couple of days ago and I thought it would be a good opportunity for me to play some football, so I'm really looking forward to it.