It would make no sense for them to trade for Winston or any other quarterback, especially once with a contract such as his. I don't think there is any way that he could pick up Shanahan's offense in a quick amount of time.
If Jimmy didn't endure the beatings that he was taking for the first three games this season, maybe he wouldn't have had to run out of the pocket and get hurt trying to get as much yardage as possible. They were just not protecting him at all. Like I said earlier. All that cap space and didn't even try to go for a premier offensive guard in Free Agency.