Manchester United will come to regret the £16 million transfer of Danny Welbeck to Arsenal, according to former Red Devils defender Rio Ferdinand.
The England international completed his move to north London on deadline day after giving up hope of becoming a first team regular ahead of the likes of Robin van Persie and Wayne Rooney.
Despite his lack of first team action it certainly raised a few eyebrows amongst both Arsenal and Manchester United fans to see the deal go through at the last minute - and Ferdinand, who left Manchester United in the summer and is now with QPR, was stunned that his former team let the striker walk into the arms of a rival.
He told the Sun on Sunday: 'I cannot believe Manchester United let Danny go, especially to Arsenal. That seems mad to me.
'He's a real threat to defenders and, if Arsenal use him right, he will be very dangerous for them.
'I think he felt frustrated at Manchester United because, even if he did well, Robin van Persie and Wayne Rooney would be ahead of him. I do wonder if they will live to regret not keeping Danny.
The blow of Welbeck's departure was certainly softened for Red Devils' fans by the arrival of Radamel Falcao on loan from Monaco. That move is said to have cost them £20 million including wages, while they will have to fork out around £45m in order to make it a permanent switch at the end of the season.
Welbeck, who is said to be taking home £105,000-per-week, meanwhile could make his debut for Arsenal against Manchester City after the international break - but before then could feature for England in their European Championship qualifying campaign opener against Switzerland on Monday.
Falcao could make his debut for Manchester United against QPR - which would see Ferdinand face his former side for the first time after 12 years at Old Trafford.