On a bizarre evening against Qarabag FK where kickoff was delayed for over half-hour and Radu Dragusin was sent off for Spurs in the seventh minute, the Premier League outfit came through by a 3-0 scoreline.
Brennan Johnson, Pape Sarr and Dominic Solanke all got on the scoresheet as the North Londoners got their European campaign off to a positive start.
However, it was not a completely perfect night for Postecoglou and the club's supporters as Gray and Son each appeared to pick up fitness issues.
Although Gray completed the 90 minutes, the England Under-21 international took a knock to his ankle during the closing stages of the game.
Meanwhile, Son was substituted in the 71st minute on the back of receiving some treatment, naturally making him a doubt for Sunday's trip to Manchester United.
What did Postecoglou have to say?
Speaking on Son, Postecoglou indicated that fatigue may have been the main reason behind his withdrawal with Spurs having played 64 minutes with 10 men at the time.
As quoted by football.london, he said: "I haven't spoke to him. He said he felt a bit tired, but I haven't spoken to him or the medical team yet."
When asked about the fitness of Gray, Postecoglou brushed aside any concerns, saying: "He didn't stop running though so can't be that bad."
Son likely to start at Old Trafford?
Barring a major issue, Son is likely to retain his spot in the team when Spurs square off against Man United on Sunday.
Aside from a substitute outing in the EFL Cup last week, the South Korea international has started every match this season, contributing two goals and two assists.
However, each of those have come in home fixtures, with two goals being scored against Everton and two assists coming versus Brentford.
Gray's starts have been restricted to cup competitions, the expectation being that the 18-year-old will drop back down to the substitutes' bench.