Celtic are desperate to hang on to Forster for the rest of the season, but his loan spell has a clause that gives Newcastle the right to recall him in January ... should they need him.
Harper could be back in action from a shoulder injury within two weeks, and that is the key to the deal.
Shay Given in on the market and allegedly available in the January transfer window.
The Manchester City No.2 has already played for Celtic, going on loan there when he was a Blackburn Rovers player, and he says he would "jump at the chance of a return to Parkhead".
But can cash-strapped Celtic afford him?