This picture was captured after the match was finished on 27 Nov. My GK was a 4 star player. Actually at that time he was a 4 star player just a sp away from 5 star and process 1 or more unassigned sp.
Click image for larger version.  Name: Match end capture 151127 match.jpg  Views: 17  Size: 87.0 KB  ID: 58364


This picture was captured today for the same match. The same GK is now shown as 5 star player.
Click image for larger version.  Name: Today screen for 151127 match.jpg  Views: 17  Size: 49.6 KB  ID: 58365

I just notice that the unassigned skill points of this player were finally suddenly automatically assigned and this made him becoming a 5 star player. I am not surprised by this and have no complaint. But it is interesting that the player is regarded as 5 star player for previous matches.

Not sure if this is a bug.