From next season, should a game in the knock-out stages go to extra time, managers will get the opportunity to make a fourth replacement.
The law change follows the success of the change seen in the FA Cup this season where sides are already permitted to get the added sub in extra-time.
That means in Champions League, Europa League and the European Super Cup matches, three subs will be permitted in normal time – with the fourth only available if the games go to extra-time.
And for the actual finals, Uefa have decided clubs can increase the number of players on the bench from 18 to 23 – giving managers the choice of up to 12 replacements to pick from.
European football’s governing body have also decided to make changes to the kick-off times in their competitions from next season.
Until now, all Champions League group matches have kicked-off at 7.45pm UK time other than games in countries like Russia where freezing temperatures have made that impossible.
But that system is being changed to introduce staggered kick-off times in the group stages in a similar way to how the Europa League has operated.
From next season matches in the group stages of both competitions will now start at either 5.55pm or 8:00pm.
All games from the last-16 onwards will kick-off at 8:00pm.
The shift to earlier kick-off times is sure to cause concern for supporters in Britain who may struggle to get to the stadiums in time for the start.
With the kick-offs set for 6.55pm continental time, there are fewer issues for those abroad finishing work and getting to matches.
But that is a bigger concern for UK based supporters, who face having to mix with rush hour commuter traffic to be in their seats for kick-off.
