What to do with my Flex

.5 ppr
Line up as of now:
QB: Phillip Rivers (hoping he passes concussion protocol)
RB’s: LeSean McCoy and Todd Gurley
WR’s: Mike Evans, DeVante Parker
TE: Evan Engram
Flex: ?
K: Prater
Def: Jacksonville
Options for my flex spot: Joe Mixon (@ Denver), Marqise Lee (@ Cleveland), Nelson Agholor (@ Dallas), and even though I can’t explain why he’s still on my team Martavis Bryant (Tennessee) .

Any advice would be much appreciated.