Reese, I am standing while taking most of these shots and I move around a lot in a typical soccer game.
I am really comfortable using my 1DX III bodies so the only mirrorless cameras I own are a pair of smaller Canon cameras purely for travel.
I use the 200-400 f4 for day games only, I like the extra stop from my 400 f2.8 for night use. And although the 200-400 focuses quickly, there is nothing that compares to the performance of a quality prime lens. The EF 400 f2.8 has saved me more than once in football in capturing interceptions and other fast unfolding changes in a play.
I keep the 70-200 f2.8 on one body and the EF 400 f2.8 on the other for most sports events. For soccer, the 70-200 comes into play when the action moves close to where I am on the sideline or when I am shooting close in action at the goal but most of the time the longer reach of the 400 is what I use.
And if you are close to the action, there will be times when even the 70-200 @ 70mm requires some creative framing to fit because players move in quickly. This football pass play was one of those cases! And it is a reason I don't use a monopod to support the lens because sometimes you have to make a fast move to avoid danger to the players and yourself. A few years ago, I was on a really poorly designed football field where there was a fence just a few feet off one sideline. The official and I had to do a synchronized jump over a couple of sliding players with both of us landing on the field because there was no place else to go to avoid the out of bounds end of the play.
Rodger
