Cesc Fabregas signing for Chelsea was one of the big surprises of the summer.
It was conceivable that Jose Mourinho may be interested in the midfielder, but it had seemed unlikely the Spaniard would entertain the choice of signing for the Blues.
Arsenal had a first option to sign the international from Barcelona, yet Arsene Wenger decided he had better options.
From a footballing perspective, Arsenal have work out fine without their former captain. They are spoilt for options in midfield, and have an array of attacking talent.
Adding him in amongst Mesut Ozil, Alexis Sanchez, Santi Cazorla and co would have given the Gunners a 'dream team' feel, but tactically he would not have been the defensive midfielder Arsenal needed to counter balance the attackers.
The Gunners are flying in the Premier League, with only a defensive injury crisis derailing them in the first half of the season. They are also on course to win a second consecutive FA Cup trophy.
Looking at their team alone they are not lacking Fabregas, and were right not to sign him, but one key event dictates that they really should have: His signing for Chelsea.
Fabregas joining Chelsea was the worst case scenario for Arsenal. He helped complete their midfield and lead them to the top of the Premier League from the season's beginning, a position they show no sign of relinquishing.
It is no exaggeration to suggest his 16 assists have helped the Blues establish a 10 point gap over Arsenal, and put them almost out of sight heading into what could have been a title decider this weekend at The Emirates.
Put Fabregas in an Arsenal shirt and the Gunners particularly in the first half of the season could have picked up extra points, and instead be leading the league.
There are of course variables to any such discussion. Would Chelsea have signed another midfielder instead? Probably. Would Sanchez have still signed for Arsenal? They do have the funds to buy both, and if they really wanted Fabregas back they should have budgeted for the opportunity accordingly.
Allowing him to join Chelsea has led to the Blues being set to win the league, and it seems to be at Arsenal's expense.
It's pragmatic to say Arsenal did not need him, but signing him purely to stop him strengthening a rival should have been entertained.
The cost is looking likely to be Chelsea Premier League title win instead of an Arsenal one, and that's still going to a hard one for fans to take, no matter their own progress this season.