Louis van Gaal should have learned his lesson when he sold Danny Welbeck to Arsenal - Do not sell to your competitors.
Welbeck scored the goal which knocked Manchester United out of the FA Cup in last year's quarter-finals at Old Trafford, just months after Van Gaal had elected to sell the England international on deadline day.
He did that in the confidence he had signed a superstar in Radamel Falcao - but unfortunately that deal did not pan out as a success.
Now with United wanting to sign a new full-back, the Red Devils approached Arsenal in an attempt to do a deal this deadline day.
The Times report that Arsenal boss Arsene Wenger has personally blocked United's request to sign the Frenchman.
SkySports subsequently reported on their live transfer feed at 5.37pm that Debuchy could end up being loaned out to Ligue 1 side Bordeaux.
Van Gaal should have seen this coming. He attempted to sign Thomas Vermaelen from Arsenal in his first summer at the club, only for Wenger to refuse to sell, reported ESPN at the time.
Perhaps he should have been more resistant when it came to selling Danny Welbeck.