Chelsea boss Thomas Tuchel revealed the decision to bring goalkeeper Kepa Arrizabalaga on for the Super Cup penalty shoot-out win over Villarreal stemmed from extensive statistical research.
There were eyebrows raised as Kepa replaced Edouard Mendy towards the end of the 1-1 draw at Belfast's Windsor Park on Wednesday night.
The two sides could not be settled over 120 minutes after Hakim Ziyech's effort for the Champions League holders was cancelled out by Gerard Moreno.
"We came (to Belfast) with so many players who did not even play a friendly match so far so this is the situation – we have to adapt and we have to, in our mindset, be as ready as we can be to do our very best."
Former Arsenal boss Unai Emery saw off the Gunners and Manchester United to win the Europa League last season, beating the Red Devils in a shoot-out in the final, but he could not make it a hat-trick of Premier League scalps.
"Last year we played a lot of games in the Europa League," Emery said.
"We won it and this year we are going to play in the Champions League, we are going to try and progress wherever we can progress and the club is ready to help us with that, keep a good squad and giving the stability they have always.
"We're going to be playing in the Champions League this year so we need to compete against those teams like we did in today's game. Today was about playing against the best team in the world. So the idea was to enjoy it but also be competitive."