The New Zealand powerhouse said he was sure that Wales would return as a force in the Six Nations following their physical display in Cardiff last November.
But he admitted he was left scratching his head as the season unfolded to prove him very wrong as Wales went on to record an embarrassing whitewash.
'I was shocked to see the results in the Six Nations Championship and how poorly Wales performed because they really gave us a battle in Cardiff,' said vice-captain Umaga.
'Wales were very physical against us, perhaps more so than England, and I really thought they had started something there and would have that flow to carry on.
'They certainly should have taken a lot of positives from it because they were very strong on that day. We threw everything we had at them and it wasn't until we scored a few late tries that we managed to secure the game.'
Wales are sure to have their hands full with the prolific Umaga, who has scored 25 tries in 46 international appearances, though managed to keep him under control for most of that last meeting at the Millennium Stadium.
The All Blacks have surprised many this week by talking of the immense physical side to the Welsh game, comparing it as more intense than that of England's, and Umaga reckons this young side is no different judging on their performance against Australia last week.
But he believes Steve Hansen's influence is bringing a new, if all too familiar, style to their game.
'Wales had a tough game against the Wallabies but they have got a very physical pack, like most of the British teams, but with Steve Hansen in charge they have now got a bit of New Zealand flavour to their defence,' said Umaga.
'Perhaps that Super 12 pattern will make things a little easier for us as we're a bit more used to it.
'But they are also a side who like to chance their arm and go out wide, they are not scared to have a crack.
'I remember that Jamie Robinson (Umaga's opposite number tomorrow) scored against us in that last game. He's pretty strong but very quick while Mark Taylor has toured with the British Lions so has plenty of experience.'
Meanwhile Umaga and the rest of the New Zealand side are under immense pressure from home to rattle-up the points against Wales.
Umaga has moved to outside centre, as one of three positional changes, to allow for the arrival of new cap Daniel Carter, one of eight new faces, who also looks set to be handed the kicking responsibilities.
'I don't think you will see too many problems in the fluidity of the side after those changes,' said Umaga. 'We have been together as a squad for three weeks now, chopping and changing, so we're all familiar with each other.
'Last week was obviously disappointing. England's defence was so effective and they really closed down our space but we have been working on that this week.'
New Zealand team: M Muliaina; D Howlett, T Umaga, D Carter, J Rokocoko; C Spencer, S Devine; C Hoeft, K Mealamu, K Meeuws, C Jack, A Williams, R Thorne (capt), J Collins, M Holah.
Replacements: A Oliver, D Hewett, B Thorn, R McCaw, B Kelleher, A Mauger, C Ralph.