Arsene Wenger reacted furiously to the Arsenal fans who criticised him for taking off Alex Oxlade-Chamberlain in the second half of Sunday's 2-1 defeat to Manchester United.
Oxlade-Chamberlain, making his first Barclays Premier League start, was by far Arsenal's best player in the first half and also set up Robin van Persie for their equaliser in the second period after Antonio Valencia had put United ahead.
Wenger's decision to substitute the 18-year-old for Andrey Arshavin in the 74th minute was met with a loud chorus of boos from the home fans, but Wenger said: "I can understand that the fans are upset about the substitution, especially when it doesn't work, but he (Oxlade-Chamberlain) had started to fatigue."
He added: "He was sick in the week. Arshavin is captain of the Russia national team.
"You have an 18-year-old kid making his first Premier League start and a player who's captain of his country and they are querying the substitution? Let's be serious.
"I've been a manager for 30 years and have made 50,000 subs. I do not have to justify every decision I make. I stand up for it."
With fixtures against Liverpool, Chelsea and Tottenham on the horizon, United boss Sir Alex Ferguson was delighted to keep within three points of league leaders Manchester City, who beat fellow title rivals Tottenham 3-2 earlier in the day.
"We said before the game that winning after City had won their game was the important thing," Ferguson said. "We did it in the right way, we played football and were adventurous and had belief in ourselves. I'm delighted with that at this time of the season.
"They are all important games, we have four massive away games and that is one out of the road."
United's win came at a cost, however. Phil Jones was carried off on a stretcher after 15 minutes after turning his ankle, Nani hobbled off in the second half and left the stadium in a protective boot, while Wayne Rooney was also hobbling at the final whistle.