Tough call. I want to say Carr, but Green is a top fantasy QB. It's really hard for me to suggest benching a top 10 fantasy QB for a guy like Carr who may or may not do well. The Chargers suck so badly, they may just run all over them and pass when they need to do so.
The lack of quality receivers in KC isn't good for Green, but Holmes and Gonzo are still going to get their looks. Last season, Green threw for 128 yds and 2 TDs / 1 INT at Denver. Then threw for 397 yards and 1 TD / ran for another TD at KC vs Denver.
The Broncos defense is better ... KC's offense is lacking WRs, so the logic says Carr. But, we all know how logic works with fantasy football.
The good thing is you don't have to decide now - but, I'd lead with Carr...