Well in 2011 he was still working for Wiggins until about 2km to go on Angliru. A few days later on Pena Cabarga he momentarily cracked an incredibly strong Cobo with one of the most impressive attacks seen in recent years.
In 2012, he'd ridden the Tour, finishing 2nd, and then had to get ready for the Olympic Road Race and Time Trial just 7-10 days later. In the circumstances it's hardly surprising that he tired pretty badly in the second half of the Vuelta. It's pretty widely accepted that when you're attempting two grand tours back-to-back, it's crucial to recover well in the first week or two after you've completed the first one. Instead Froome was having to prepare for a home(ish

) Olympics just a week after the biggest achievement in his life, finishing on the Tour podium, and enduring all the hassle and pressure that went with it.
I mean, as excuses go, I'd say Froome has a pretty good one for struggling in the second half of the Vuelta! Let's not forget that after the first week of the Vuelta most Contador fans had thrown in the towel and were handing Froome the red jersey.
There are six mountain stages in this year's Tour and just three in the first 17 stages. Harder than 2012, sure, but let's not pretend that it's a monstrous parcours this year because it isn't. There's just no evidence either from the Vuelta 2011 or the 2012 Tour to suggest that Froome will struggle badly at the end of this year's Tour. I mean it's the complete opposite really. His recovery is very good. Froome was being beaten by the likes of Thomas Peterson and Bart de Clercq at the end of last year's Vuelta. That isn't going to happen in this year's Tour! If you're expecting Froome to crack horribly as Contador saunters to victory then you're going to be very disappointed. It defies all common sense, logic and everything that we've all seen with our own eyes, including Alberto's not so special form so far this season.