Birmingham manager Steve Bruce insists only a 'crazy deal' could tempt him to sell defender Matthew Upson next month.
Upson is out of contract at the end of next season and has been linked with a move to a Premiership club in the January transfer window.
Tottenham are among those linked with the former Arsenal centre-back. But Bruce, whose side top the Coca-Cola Championship by eight points, wants to keep the 27-year-old at St Andrews.
Bruce said on Sky Sports News: 'Of course people are going to court him because he has only got 18 months [left on his contract] - but why would I want to sell my best player?
'We are going along nicely, and I want to see Matthew Upson play for us and take us where we want to be.
'We don't want him to go anywhere. He has only got 18 months to go, but it is going to take an absolutely crazy deal to even consider letting our best player go just when we need him.'
Upson is Bruce's chief fitness concern before tomorrow's home encounter with Luton - when Blues will hope to extend their advantage at the top of the table to 11 points.
Upson scored but was then substituted in the win 2-1 Boxing Day win over Queens Park Rangers after complaining of tightening around the groin. He will face a late fitness test.
Midfielder David Dunn is all but certain to miss out, despite having returned to training following a recurrence of long-term hamstring troubles.
Blues will face a Hatters side needing points to avoid being pulled into a relegation fight, after their inconsistent form continued with a 4-1 defeat at Colchester on Tuesday.
Yet with Birmingham having won 12 of their last 13 games, Luton boss Mike Newell insists all the pressure will be on the hosts.
'We go there as underdogs,' he told his club's official website.
'Every Birmingham City fan expects to turn up on Friday night and win - so the pressure is on them if it's on anyone.
'We will treat the game like any other away game and respect the opposition, but try and get a result there.
'All we can do is go there and give it everything we have got with what we've got available and see what happens.'
Newell has doubts over midfielders Ahmet Brkovic, Steve Robinson and David Bell but will give all the chance to prove their fitness.