Sammy is at a big disadvantage having missed OTA and Most of Training Camp and is still behind. You have to remember he is still a young receiver and isn't going to just come in a pick it all up.
They bye week will give him some time get more comfortable and get on the same page as Goff.
We have seen some great hands and the ability to make difficult catches and defense seem to want to keep him out of the game. We also see that he has trouble releasing from the LOS which is a skill thing for him to work on.
Overall we need to resign him to make this a good trade.
Also you can't catch the ball if you aren't targeted which has also been an issue.