The Republic of Ireland international arrived at the Riverside on a temporary three month arrangement from Preston North End during Gareth Southgate's reign.
The precise terms to extend St Ledger's stay on Teesside have yet to be revealed but, after suffering the agony of missing out on a place at next year's World Cup with the Rebublic of Ireland last week, the centre-half is focused playing Premier League football with Boro next season.
He'll be staying here, revealed the manager. As far as I am concerned that deal is done. That's what I have been told.
Tomorrow's match at basement team Peterborough, the club where St Ledger began his career, offers an ideal opportunity to register the first victory of Strachan's tenure.
St Ledger has impressed Strachan with his attitude on and off the pitch.
While some managers rested their players on their return from World Cup play-off duty, the Boro boss had no hesitation in fielding the 24- year-old against Nottingham Forest last weekend.
We've not got a big squad to chop and change I'm not in a position like Alex Ferguson who can maybe leave his Irish players out,'' said Strachan.
Sean was fine on Saturday.
As a player in big games your emotions go up and down so physically it's difficult. Disappointments, elation you have to deal with the lot.
He'll learn that. It's nice to see your players doing well but now he's at the stage where we look at how do we make him better.
St Ledger's taste of playing at the highest level has left him hungry for more and he looks forward to one day testing his mettle in the Champions League.
I would like to make a permanent move here without a doubt,'' he insisted. Coming to a club with this stature and ambition is definitely something I want to carry on.
I want to play in the Champions League and that means playing twice a week. I am very impatient and I wanted a World Cup place now but you have to try and move on and set yourself another goal, which right now is getting Boro promoted and back to the Premier League.
At least we are not in midtable mediocrity and there is a goal to aim at.
St Ledger may be eyeing the top spots but Boro's current position is 11th in a league of 24 teams. Victory at Posh, however, could send Strachan's side back into the playoff spots.
Confirmation that Emanuel Pogatetz is fit will allow Strachan to name an unchanged back four against Mark Cooper's side. St Ledger isn't sure if his defensive colleague is brave or just mad to play with a head wound and a protective mask that guards his fractured cheekbone.
It depends how much his appearance bonus is because he would do anything for it,'' he joked.Yeah Poggy is a bit mad but all the players would want to do the same and just play. I have played alongside some tough boys but never anyone who has played with a fractured cheekbone and stitches. It is just frightening and it shows just how much he wants to play for the club and do well.
Strachan added: It makes me nervous watching Pogatetz but he's fine. If it makes you play like that we should all be wearing masks!