A three-man backline against Mattocks-Adi-Melano would get torched.
As much as I want to stick with exactly what is working as of late, I think Portland is the caliber of team we have to gameplan around a bit. They are fast and wide up top, and have excellent attacking mids in Valeri and Nagbe.
If there's ever a game to sacrifice possession for position, it's probably this one. I'd have us sit back a little bit and counter attack. Start Mendoza on the wing and move McNamara back inside for this one.