The Bath veteran is aware of the daunting challenge Wales face as they attempt to win their first game in this season's tournament.
An opening day defeat to Italy was followed by losses to England and Scotland.
Ireland, on the other hand, easily overcame Scotland, then Italy, and most recently dispatched France with a gritty performance at Lansdowne Road.
And recent history between the Wales and Ireland suggests the travelling fans will be in confident mood as kick-off approaches.
Ireland have not lost in Cardiff since 1983, and will not expect that record to be broken this weekend. In the eight games during that period, Wales have managed just one draw.
'This is the best side that Ireland have had in as long as I can remember,' said Humphreys.
'They are the best team in the championship, and you would bound to feel confident if you were in their position.
'They will come to Cardiff wanting to do the business.
'They've got a very happy bunch of players performing at the top of their potential, and it's going to be a massive challenge for us.
'I think it will be a bigger challenge than playing against England. In my opinion, Ireland are currently playing better than England, and they've also got the best player in world rugby (O'Driscoll) at the moment.'
O'Driscoll has scored 99 points in 36 tests. The Leinster centre will lead out the Irish at the Millennium Stadium on Saturday.