Arsenal manager Arsene Wenger admitted he was "a bit angry" to learn that Tottenham star striker Harry Kane was rejected by the Emirates club as a youngster.
Kane spent a year at the Arsenal academy before being let go. He eventually found his way to city rivals Tottenham, where he exploded onto the scene with more than 30 goals in his first full season with Spurs.
"I didn't know, I read it in the papers," Wenger said. "I found it quite funny, you know, and you are always a bit angry as well because I asked: 'Why did he go?' But at that age, boys can move here and there."
Earlier on Friday, Wenger said he would not consider signing a player from Tottenham, even Kane.
Wenger's side face Spurs in the North London derby this weekend, having lost 5-1 to Bayern Munich in the Champions League in midweek. The Gunners' squad depth has been criticised this season, with Wenger only having signed goalkeeper Petr Cech this summer, but the Frenchman insists that there is one team he could never consider buying from.
Former Tottenham captain Sol Campbell did move from White Hart Lane to Highbury, then home of Arsenal, in 2001 but that was as a free agent after his contract at Spurs had expired.
Asked about the possibility of signing Kane, who has 26 goals in 45 games over the past two seasons, Wenger said: "He has great qualities and he will make a great career. But once a player is at Spurs you don't even consider him any more."
On facing a Spurs side who beat Anderlecht 2-1 in the Europa League, he added: "They are a side that are strong defensively and can play at a a high pace in a committed way.
"They have done well. They have lost only one game. They have a few draws. They have always in my memory had strong teams. It will be a tough opponent just like every year."
Despite the heavy defeat to Bayern, Cech was praised for his performance in Munich and Wenger believes that his new goalkeeper will go down as one of the best to play in the Premier League.
"I believe there is no coincidence," he said. "It's just class, consistency and quality. And knowing him well after a few months I am not surprised. He analyses everything.
"He is gifted, super-talented and he is one of the greatest goalkeepers ever seen in this country.
"He plays in a position where age is less of a restriction than in any other job. I think 37 or 38. Some go longer but once you start to have a 'four' the intensity is more difficult. Van der Sar was close to 40 and still doing well."