While he came off in New Plymouth to have a Head Injury Assessment, he's concussion-symptom free.
The medics have no issues with Dagg's head but need to be satisfied that he will have adequate range of movement in his knee to be able to get through 80 minutes at full speed against the Springboks.
This is finger's crossed territory for the All Blacks because however much they will roll with what fate delivers, they want Dagg to be available for this one.
They need his experience and his leadership.
They need his ability under the high ball and his booming right boot.
And maybe above all else, they need his presence on the wing to prevent the Springboks from forming the impression that the All Blacks are vulnerable in the backfield.
A new look Springboks side is coming to Albany undefeated in 2017.
They have underlying confidence and no doubt a little frustration, too that they didn't manage to land the killer blow in Australia last week and find a way to break the 23-all deadlock in the closing minutes.
And while the Boks have reached these new heights with a more balanced look to their game plan: with a greater desire to move the ball and attack on the edges of the field, the All Blacks are expecting them to tighten up in Auckland.
"When they come here we are expecting them to want to play," said All Blacks assistant coach Ian Foster.
"But I would imagine they will be looking at last week and be using the aerial ball more than they anticipated. But you know that comes with risk and reward for them, because if we do what we want to do with those high balls, then we have got great opportunities to attack as well.
"So it is a two-edged sword that tactic."
The selection mix for the All Blacks back three is all important in this test.
It is an area they have to get right in the sense they feel that the trio they pick is able to deal with the high ball, counter attack, defend and finish.
It's a broad remit and the beauty of Dagg is that he individually ticks all the boxes.
If he's passed fit, it is likely he will be on the right wing, with Rieko Ioane on the left and Damian McKenzie at fullback.
That's arguably the combination that gives the All Blacks the greatest array of skills and the greatest sense of confidence.
If Dagg isn't available, the All Blacks will be picking three from McKenzie, Nehe Milner-Skudder, Waisake Naholo, Ioane and David Havili.
Between them, they have a total of 36 test caps, with Havili yet to make an appearance at this level. It wouldn't matter which combination the selectors settled on, the total experience of the group would be light.
And without Dagg, it is almost certain that the Boks will look to kick high and contest with an element of confidence - it could be a tactic that plays well for them.
McKenzie is brave in the air, but his lack of size - he's 1.77m and 79kg - is relatively easy for opposition teams to expose if they can create a jumping contest.
Naholo isn't renowned for his accuracy in that area; Milner-Skudder is strong but relatively small as well and Ioane hasn't really faced a serious examination of his skills in that area during a test.
