Not wishing to be overly pessimistic, but any investment during the window would have to be on the basis that Bielsa is prepared to enter into some degree of squad rotation, which he hasn't shown much appetite for to date (in the PL or Championship days). If that's not part of the plan, all we will end up with is a bunch of reserve players getting no 1st team time until injuries/suspensions force Bielsas hand (as has been the case with Meslier some time ago and Struijk more recently), never an ideal time to introduce "new" players into what is otherwise a settled 1st 11.