Of course, now he's wearing the maglia rosa, Nairito can suck the wheel of any attack he likes.
The problem with a backloaded Giro is that there's little reason being in form for the start of it. If anything, the illness has helped Quintana in this respect as he's now peaking just in time for the big epic mountains, while riders who looked really strong in week 1 (Urán, Evans) are fading, and the stages to come look like they will distance them.
That said, it's still been the best Giro since 2010, and better than any GT in 2013. Nairito may seemingly have it sewn up, but now Movistar are charged with defending Rosa, the strength of their forces on the stages to come could be challenged, probably most likely by Ag2r. I think Nairo will be able to control the race from here on in, he has enough left in the tank and his climbing level is the best in the race, but still, the battle for 2nd and 3rd should be very fun with a lot of contenders quite close to one another, especially with a TT like Monte Grappa to come.
And the thing with Nairito is that he blows the race apart, sometimes not when you expect it too - attacking more than one climb out in the Tour last year, three climbs out when he won the Route du Sud, and even on a descent here, controversy or no controversy, Quintana attacking on a descent is something that people don't necessarily expect. Abarcá are brilliant at opportunism on the big occasion even if they occasionally court controversy with it - they managed to win a Tour with Óscar Pereiro that way, nearly won a Giro with David Arroyo with it, managed to insert Luís León Sánchez into a GC mix he had no business being part of, albeit temporarily, in the 2010 Tour, were a key part of the Froome isolation stage in last year's Tour (although they failed to capitalise on the situation they developed) and the Fuente Dé mugging, and picked up a bunch of stage wins and leader's jerseys in unexpected places with the likes of Kiryienka, Intxausti, Visconti, Lastras and Costa. It isn't surprising that they might try something unusual or push their luck (can't we just imagine them in the car saying "they said that they'd have a red flag, but did they say it was neutralised? Nobody actually specifically said it was neutralised, did they? Nairo, try pushing on and see what the race directors say!"?). And let's face it, Nairito was strong enough and talented enough to make it work, gained a bunch more time on the final climb, and it might have won him a Grand Tour. Can't argue with the end product.