Arsene Wenger says he doesn't know why Chelsea allowed Arsenal match-winner Eddie Nketiah to slip through their fingers.
The former Chelsea youngster proved the difference on Tuesday as the Gunners came from behind to beat Norwich 2-1 after extra-time and take their place in the Carabao Cup quarter-finals.
Wenger, who made 11 changes from the side that won 5-2 at Everton on Sunday, turned to Nketiah with five minutes to go and the England Under-19 responded with an equaliser just 15 seconds after entering the fray.
"I don't know why exactly Chelsea let him go or if he decided to leave, but young players more and more nowadays travel from one club to another. We're happy to have him," said Wenger.
"I can't remember a young player having such an impact in a game like that. Until he came on we lacked ideas and creativity."
Nketiah was a schoolboy with Chelsea until 2015, when he was released for being too short. The 5ft 8in striker was then taken on trial by Arsenal and on Tuesday scored his first senior goals for the club - the second with his head.
Henry, Arsenal's all-time leading goalscorer and now a Sky Sports pundit, tweeted his congratulations to Nketiah.
"What a night for EddieNketiah9. So happy for him and not surprised at all!" he wrote.
