I'm really not all that down on Gabriel - of all the players I think he will show major improvement over time. He's not the fastest player, but he's not slow either - was running a 4.54 40 yrd dash coming out of college.
The past knock on Gabriel has been that he's not a great route runner - and that's something that the Patriots - specifically with Branch - liked to do - i.e. run a deep route. So unless there's vertical separation - and thus far there hasn't been that much - at least not deep with him - he's not going to do more than keep a CB occupied, leaving the SS and FS to collapse.
(Some of those "underthrows" by the way looked very much to me like Gabriel may have turned the wrong way or otherwise miscommunicated with Brady)
Jackson is indeed a burner - but as I said before, while I advocated for drafting Jackson, it was with the thought that he'd need a year to develop like nearly every rookie does. And that was before he injured his hamstring - so expecting him to tear up the stopwatch like he did in the combine - and still be a credible threat to actually CATCH the ball, isn't something we should count on.... maybe he can contribute in the playoffs, but a guy who thrives on speed with an injured hamstring is not a good combination.
Gaffney's not a bad signing but doesn't do anything to address the deep threat - he averages less than a TE in average receptions - he's a possession WR and if he plays like he is capable, its like having another Troy Brown on the field.
So while its not like we've signed a bunch of replacement players, we don't currently have a credible deep threat - Watson and Thomas are the best deep options we have - but at 250lbs one has to question their breakaway ability and endurance - but of course even using them deep would fall under "creative playcalling" and the vast majority of fans seem to think that McDaniels playcalling is just fine the way it is.