Son has been ever present this season, starting in all except the Carabao Cup tie at Coventry when he came on for the last half hour with the result in the balance.
But the 32-year-old is a doubt for Sunday's game at Manchester United after coming off late in the 3-0 win against Qarabag in the Europa League on Thursday with fatigue in a hamstring muscle.
‘Whether that’s an injury or just fatigue we’ll have to see,’ said Spurs boss Postecoglou, who has loaded more minutes on his captain than he wanted because of injuries to forwards Richarlison, Wilson Odobert and Dominic Solanke.
‘I’d have wanted to ease his workload in this early part of the year,’ said Postecoglou. ‘He has certainly played more than I want him to.
Son Heung-min is a doubt for Tottenham's clash with Manchester United on Sunday
‘The idea of signing Dom, bringing in Wilson and extending Timo Werner’s loan was to manage his load because he’s got international football as well.
Son, who will be assessed on Saturday, is also South Korea’s captain and rarely misses a game in international football. He played every minute of two World Cup qualifiers last month.
‘There’s no chance I’d ask him not to play,’ said Postecoglou. ‘I understand how important it is for him.
‘We can all look in cold harsh light and think his club football will benefit if he doesn’t play for his country but one day he won’t be able to play for his country and I wouldn’t want him to have regrets that he missed the opportunity to play more.’
With Richarlison and Odobert still out injured, Werner, Dejan Kulusevski and teenager Mikey Moore would come into Postecoglou’s thinking if he were forced into a change.