he`s gone in goal in place of your injured keeper
15 Titles
10 Runner-up
5 Champions league
2 Runner-up
4 Cups
2 Runner-up
1 Treble
According to my limited experience on this, GK injured during a match is not as bad as it is looked. The other player(s) will step up and do some pretty good GK works. That's why some manager does not employ backup GK.