Purito is always a guy who can do it over short and medium mountains, but over the big long ones it's always going to be the last 2km for him; he has good burst but less endurance when attacking. We saw in 2008 from when he attacked, attacked some more and attacked again but always ran out of gas (usually in the face of pressure from a totally CERAd up Emanuele Sella to be fair) that he wasn't suited to it. Similarly, he stuck with Contador longer than Valverde on Angliru, but Valverde could catch and pass him.
Purito's lack of TT will always harm him, and his ability to crush for 1-2km makes him a threat in hilly and medium mountain races. He is always a figure to keep an eye on for the GC, but he isn't a true GC threat at the GTs, you would say. After all, his chronic TT put paid to his 2010 Vuelta, his inconsistency his 2010 Tour, and lack of ability to attack from distance always means that it's hard for him to win back the time he's lost - as shown in the 2011 Vuelta when he tried in a wide variety of ways to win back the time he lost on the grinding climbs, and only succeeded in blowing himself up on the next mountain.
Each time he comes to a GT he comes for the GC, and regularly spends a bit of time at the top end, but falls away, because ultimately he's quite limited as a rider.
Do not blame Purito for riding defensively today and for only attacking near the end; it's just what he's got in him. Blame the other riders being so timid, and the course being chocked full of medium mountains up until the last three days, for meaning that he's still doing that with the leader's jersey on on the penultimate day.