FC Porto's long unbeaten run stretching back almost two years came to an end in Barcelos on Sunday night as Gil Vicente beat the champions 3-1.
A pallid Porto were unrecognisable for most of the match, while that takes nothing away from an excellent all-round display from the hosts.
Claudio's early header flicked over Porto goalkeeper Helton to give the Gil the lead set the alarm bells ringing for the Dragons, and on the stroke of half time a penalty given away by Otamendi gave Claudio the chance to score his second goal.
The centre-back did not waste the opportunity and Paulo Alves' side went into the interval with a comfortable lead.
Things went from bad to worse for Porto in the 52nd minute as André Cunha showed excellent skill and a cool head to turn his marker inside out before firing into the corner of the net to make it 3-0 in front of the ecstatic crowd.
Substitute Belluschi brought some zest to Porto, and the Argentine's perfect throughball was smashed into the top corner by Varela to reduce the deficit.
It was too little too late, however, and Porto left the field a beaten side for the first time in 56 Liga ZON Sagres matches.