Last summer's deadline day seems a long time ago now, yet it may just have been pivotal in the Premier League title fight.
Arsenal, as well as buying Mesut Ozil, were looking at securing Demba Ba on loan from rivals Chelsea - deal which at one point appeared likely.
That was until Jose Mourinho realised Arsenal had signed Ozil, and pulled the plug on the deal, fearing he would be making Arsenal 'too good'.
He told reporters at the time: "I did not accept Arsenal's offer for Demba Ba because added to their signing of Ozil, they would have been title contenders."
Instead, keen to trim his troupe of strikers from four to three - Jose Mourinho made another late, fateful decision.
He sent Romelu Lukaku on loan. The destination of Everton hardly mattered - what has been crucial has been that he has not been at Chelsea.
The decision to let Lukaku go instead of Ba has been a costly one. Ba has made just three starts in Premier LEague and Champions League all season, and as last night's Champions League game showed, he is viewed by Jose Mourinho as a persona non-grata.
Lukaku instead was sitting at home watching the game on television, about as big a waste of his talent as you could hope to find.
Chelsea have dropped crucial points in recent weeks thanks to the inefficiency of their strikers, with Torres failing to get a shot on the target from 11 shots in defeats against Aston Villa and Crystal Palace.
Lukaku meanwhile has gone onto score regularly for Everton, and fire them into Champions League contention.
If Mourinho was not so worried about Arsenal back on deadline day, and more concerned with his own squad - he may not have backed himself into making the big error which looks set to define his first season in charge.
Yes, Arsenal would have been a force with Demba Ba in their ranks, who may himself have caused Mourinho plenty of regret.
But would an Arsenal side with Ba, have been stronger than a Chelsea one with Lukaku?
Mourinho was worried that it would be so, yet that lack of faith, or fear - may just have cost the Blues silverware this campaign.