Afrank said:
I think it could be likely he mistimed his peak slightly. Timed it more around Cali then the Tour.
But a large part of it, sadly, I think could be that he isn't quite as strong yet as his result last year seemed to indicate. The absence of mountains, excess TT km's, and Sky's steady tempo climbing did play to his advantage last year.
(But I am holding out hope that he'll be back, this isn't the last we will see of him in GT's.)
I agree, especially with the bolded bit...
Last year had a parcourse and field that was very favorable to Van Garderen (and, even more so for Wiggins). The long chronos, dearth of truly decisive MTFs, and nearly all attacking climbers either DNS, crashed out in the first week, or lost too much time in the first week meant it was mainly just a steady pace that fit Van Garderen perfectly.
Plus, there were no real expectations for him. I think there was even talk of him pulling out at the second rest day, which is common for young, promising riders. So depending on how he develops over the next couple of years, and how routes shake out, he could certainly be a contender.