The Patriots did not have cap space available to go after players early in free agency, and that is when premier free agents are signed. That cap space only became available when players like Hightower opted out, and at that point the free agency cupboard was bare. Signing a familiar name is no guarantee he will immediately make an impact either, between time taken to learn a new offense and terminology, and whether or not he is in football shape after no training camp.
NFL Trade Rumors complete list of 2020 NFL Free Agents broken down by position. The 2020 list will be updated throughout the offseason as moves are made.
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This, and the Patriots are relying on second year players and rookies to fill the void, and it's not surprising or an indictment against them that Bill is integrating them in slowly, while playing to his QB's strengths.
There is reason for some optimism:
1) Gunner will help when he's back in week four.
2) Harris, although a RB, will help the passing attack when he's back in week four.
3) Asiasi took his first snaps at a hard to learn position and should contribute more soon.
4) Keene was injured but could be able to continue down the road.
5) Izzo for what it's worth looked improved.
6) Young receivers will continue to improve and get in better sync with Cam.
This offense only needs 3 receivers per game to be effective if the line and RB's stay healthy, and if either Asiasi or Keene becomes a viable threat. It won't be conventional, but the Pat's passing attack could be decent/more well rounded by December, but if the newbies don't develop it could also suck.
I'd rather see what we have this year and save the cap for next year, unless someone is available via a trade on a reasonable multi year contract.