I'll throw out an opinion to see if it sticks: I think right back could be the key to unlock our entire formation/personnel.
Everyone agrees that improving the defense is an offseason priority. But everyone is focusing on our defense up the middle, when an extremely sizable portion of our defensive struggles were down the wings. Both Matarrita and Allen have struggles with effectively tracking back, and Vieira tried multiple players at RB to correct this issue (White, Hernandez, Iraola) that were massive failures.
A quality right back would do a ton of things for us tactically. First, it would obviously improve our defense down the right wing. Second, it would likely improve our set piece defense. Third, it would unlock Matarrita to realize his full offensive potential, with less of a concern placed on ensuring defensive coverage. Fourth, it would improve our passing out of the back. Fifth, it would allow us to shift into a three-man backline comfortably whenever necessary, which would also allow Chanot to step into a sweeper role and maximize his impact.
In contrast, a great CDM would also be a good addition, but it wouldn't solve our issues with defending down the sidelines, it wouldn't really unlock Matarrita to go forward on offense, and it wouldn't help with formation flexibility.
I'm not saying we should sign a DP RB, just that it may be an extremely critical spot. It may have been our worse position last year.
Here's what I'm imagining:
If we can grab a quality defense RB, we could afford to find a solid yet reasonably priced CM/CDM to play next to Pirlo and have a very strong defensive shape with the ability to pass out of the back. Plus, we can make sure we leverage our DP spot into a player with an attacking player (any of the top four). This roster probably still needs another attacking player and another midfielder for depth, but I would be very happy with this for an opening day starting lineup.
To throw out some names for the spots, I've brought up Alvarado for RB a few times, and Will Johnson would be a good CM/CDM option. Any other suggestions?