This one happened to me in the CL Finals this season (what timing!), luckily in my favor: I started the match employing 4-5-1v defensive against an equal Q opponent. They scored at the 10' mark so I made early substitutions and changed to 4-4-2 wide attacking.... And immediately tied the game. I made another sub at extra time and won the match and my first CL trophy with the same player via free kick.

I guess the game encourages us to make tactical changes during the match. Or its all just random nonsense.