Garnacho is becoming their main creative outlet now, either he is kept quiet by Walker or pulls out injured. I believe without him and Fernandes and Hojlund, there should be little goal threat. Garnacho, despite being an odious sort, is quite effective occasionally.
I'm not a fan of derby build up, tend to avoid it until the day, but Rodri should have Kovacic in the middle with him in my opinion, as it is here that United will attempt to kick their way through us, as they little other option now.