Fourth substitute trial to be extended to four Uefa tournaments

Alvaro Morata coming on for Cristiano Ronaldo in extra time at the Club World Cup last year was the first fourth substitution in football

The trial for a fourth substitute to be allowed in extra time will be extended to four Uefa tournaments this summer, the governing body has announced.

Teams at the women's Euros and Under-19 Championship, as well as the men's Under-21 and Under-19 Championships, will all be allowed the extra change.

Real Madrid's Alvaro Morata became the sport's first fourth substitute at the Club World Cup last year.

Uefa will also continue to trial the 'ABBA' penalty system.

It was first used at the women's European Under-17s tournament last month, when Germany beat the Czech Republic 3-2 in a semi-final shootout.

How does ABBA work?

As the current system stands, teams take turns in a shootout, with the choice of who goes first decided by a coin toss.

For example, team A goes first, then team B, then team A again.

The new system is called sees team A followed by team B - before team B goes again. Team A would then get two successive penalties, a little like the tie-break in tennis, and so on until there is a winner.

A coin will still be tossed to decide who goes first.

Has a fourth sub been used in Britain?

Yes. The Football Association announced last summer that it would permit an extra substitute in the latter stages of the FA Cup, from the quarter-final on.

Manchester City were the first team to make use of it in England, as Kelechi Iheanacho replaced Raheem Sterling on 105 minutes in the semi-final defeat against Arsenal.

In Scotland, Ayr United benefited from the rule change in their Scottish Cup fifth round win over Queen's Park.