Yang played his last game in SK playoffs in early November, and the previous SK play off game was almost a month before that - that ended Yang's SK season which had started in spring 2024.
So whilst Yang joined Spurs on 1 January he'll have joined pretty unfit and needing a 'preseason' to get fit to play which I'd guess will take 4-6 weeks, suggesting he'll start playing in February. Of course that could be incorrect, but I'd be surprised if he arrived as fit as is needed to play in PL.
Yang does not qualify as a List B u21 player and with only 3 changes allowed to EL squad at end of January transfer window, I'd guess he won't be registered in EL, so he'll be playing )PL and domestic cups this season, so no 'easy' matches to try him out in. Maybe one or two u21 matches to start ?
So could be a 'race' between Yang and Odobert as to who is fit enough to play first ?