The Broncos signed Manning and traded Tebow to the New York Jets this week.
Robertson says he thinks the moves show that Tebow was not appreciated.
"I think the Denver Broncos treated him shabbily," Robertson said, via Mediaite.com. "He won seven games, he brought them into the playoffs, for heaven sakes. I mean, they were a nothing team. He rallied them together with spectacular last-minute passes and, you know, when they beat Buffalo - I mean, Pittsburgh, excuse me - it was a tremendous victory. And you just ask yourself, OK, so Peyton Manning was a tremendous MVP quarterback, but he's been injured. If that injury comes back, Denver will find itself without a quarterback. And in my opinion, it would serve them right."