With Arsenal contriving to cock up , there was that potential for Swansea to give a sucker punch .
Arsenal arrived when Ashley Williams reacted to Gyifl Sigurdsson 's cross to put the Swans ahead .
With Arsenal contriving to cock up , there was that potential for Swansea to give a sucker punch and it arrived when Ashley Williams reacted to Gyifl Sigurdsson 's cross to put the Swans ahead .