I can see your argument, but I don't see a penalty getting called there too often. Even after watching it over and over, it doesn't appear to me to be anything obvious.
That and the fact that there were two other defenders right there. That one had a low probability of being complete regardless.
i agree with you guys--it would have been hard for the refs to see it with all of the other action going on. and it was low probability. but it was more than just incidental contact as it actually affected gronk's ability to go for the ball. here's what he said afterward:
"Was I held? I don’t know," Gronkowski said. "I felt like I was held because I couldn’t even jump. I felt like (Broncos cornerback Aqib Talib) had me. He’ll probably text me later and be like 'Yo, I was holding you, bro.' I felt like he was, but sometimes you go back and look at it and he wasn’t. It is what it is, though. I think the ball was going out of bounds on that, anyway, too, but we fought on the next drive and we did what we had to do to score."
USA Today: Patriots' Rob Gronkowski thought he was held on crucial fourth down
gronk usually goes out of his way not to make excuses or complain (even in the quote above), so if he says talib's jersey tug kept him from going after the ball, i believe him.
anyway, talib got away with it, so it was a savvy veteran move by him.