The 23-year-old striker ran out at the Hong Kong Stadium on Wednesday a day after learning that his first coach, Josef Schulz, had lost his battle with cancer at the age of 61.
Altidore told the Sunderland Echo: "For me, it was always going to be a difficult game. It was probably the hardest game of my life because on Tuesday, I had some bad news.
"The guy who got me into football lost his fight with cancer. Everything I've known has come from him, so it was a really difficult game.
"But I was happy that I could play and show the guys that I'm committed. That was the biggest thing for me, to show I care and that I'm committed.
"I'm a private guy, I haven't really talked about it. I didn't care if anyone knew about it.
"But these guys have been working so hard that I owed it to them to go out on the pitch and give something to them."
Schulz spotted the former AZ Alkmaar frontman's talent as an eight-year-old in Florida and worked with him at both the Boca Raton Soccer Club and the Schulz Soccer Academy before he joined New York Red Bulls.
Altidore played his part in a hugely encouraging win over Spurs, and might have opened his goal account shortly after the break, only to pass up a glorious opportunity.
He said: "I had a few chances, but I'm just happy that I can get these games in."
One man who did find the back of the net was 33-year-old defender Wes Brown, who marked his return from more than a year on the sidelines with his side's second goal to confirm his fitness and further persuade manager Paolo Di Canio that he has a part to play next season.
Di Canio said: "I have to be honest and say that with a team I wanted to rebuild, I thought at the beginning that he was not on my list for the future.
"After one year and two months out, at his age, I couldn't start thinking about a player who I didn't know if I could rely on.
"I spoke to him and was clear that he wasn't on the list. But I'm very happy to tell him now that he's completely on my list. He has got experience, quality, desire and he can help the others."