Start Vance McDonald in the flex?

So I am tilting between:

Derrius Guice vs. Philly and Christian Kirk vs. Detroit and am not sure either will have a good game, but you never know - particularly with the in-conference matchup between Washington and Philadelphia.

I added Vance in a later round and feel like he might be pretty solid against New England. Therefore, am wondering if he’s the safest bet to throw in the flex this week while we wait and see what Guice and Kirk can do? I already have Kittle in the TE slot.

I’d go Kirk. Think they will be playing from behind so think he will get a lot of targets.