From CFO Maestri on the Q&A call with analysts:
"2:15 pm: We had the benefit of a 14th week, but this was offset by several factors including less channel fill than last year and a one-time $548 million patent judgment receipt last year."
Channel fill is fairly irrelevant (whose fault is it that your distributors don't want more of your stuff "just in case"?) and the cash is also fairly irrelevant - what matters for momentum is the number of units shifted and that's lagging everywhere except iPhones (and, if you trust them, the Watch).
http://www.macrumors.com/2017/01/31/q1-2017-results/