the 'gates' or 'detents' for the thrust levers are (ignoring reverse) IDLE, CLB, MCT/FLEX and TO/GA.
The thrust lever range you would use for a manual thrust approach is only likely to be between IDLE (naturally) and CLB (max climb thrust). Thus you would not move the levers as far as any of the gates.
Anyway, I think that after disconnection, A/THR is only re-engaged if the thrust levers are moved into the TO/GA gate (or the pb is pressed), so you could even use CLB or MCT thrust on your visual approach without re-engaging the A/THR.
Although if one needed MCT during a manual thrust, visual approach, I would suggest that selection of TO/GA would become a good idea in very short order...
