If AD thinks he can force a trade, history is not on his side. Aaron Donald won't be the first player to threaten to sit out, or to actually go through with sitting out a significan portion of the season, or an entire season, in a contract dispute. Get on Google and see how many of them got traded vs. eventually signing with the home team. Go ahead, it won't take long. I'll wait right here...
OK done? How many players got traded after holding out? __________
How many signed with the home team? __________
So let's look at how hard it would be to actually pull off such a trade to help explain the numbers above. A lot of things have to line up.
First off, a team would have to be willing to pay AD what he wants. No trade could go through without AD agreeing to a contract with his new team first. There are probably some teams that think that AD is worth more than Rams are offering him. But certainly not all teams. Would some team offering just $1M/year more than the Rams be worth it for AD? Maybe, but probably not. They'd need to think that AD is worth what he is asking. How many teams is that? Of course that depends on what he is asking. But its not like 31 teams would be willing to pay his price.
Second, any team that happens to agree that AD is worth what he is asking would have to have the cap space to sign him. Not every team can do that. But for the sake of argument, lets say that any team that thinks AD is worth his asking price would make room in their cap.
Third, they'd have to be willing not only to pay AD what he is asking, they'd need to give up a LOT in return. I'd think 2 first round picks is the starting point or its simply not worth it for the Rams. So the price for AD is not only his huge contract, but a ton of draft capital. How many teams are willing to pay that price? It's getting very expensive...
Fourth, there will be many teams that the Rams simple won't trade him to. Certainly not any team in the NFC West. Likely not any NFC playoff team or team on the verge of the playoffs. The last thing the Rams want is to face AD in the playoffs and watch him sack Goff three times. This may very well apply to some teams in the AFC as well.
Fifth, aside from not wanting to trade AD to a team that they may face in the playoffs, they just won't want to trade him to a very good team. They'd want those draft picks to be in the top half of the first round, not the bottom half. This not only cuts down on teams willing to pay the price, but also those AD is willing to be traded to. Somehow I don't see AD agreeing to be traded to the Browns...
The number of teams that would be willing to meet AD's contract demands AND give up the draft picks AND the Rams are willing to trade to AND AD is willing to play for just wouldn't be that large.
Last point, and the most important. Jarod Goff. If AD were to demand a trade if tagged and the Rams caved in and traded him to the team willing to pay him the most money, why wouldn't Goff go down that road too? What about Gurley or any other superstar who wanted a new and bigger contract? It would set a terrible precedent that would haunt the team for years. Again, this probably explains the answers to the questions at the top.
Oh wait... There is one more thing