He's a lock as the #5/6... There's NFW he's even close to being ready for the #4 role; that's Meyers' to lose...
I'll try to be more clear.
There are 3 WR's who will get almost all the reps unless there is an injury, or perhaps even 2.
WR #4 is either a STer or perhaps a developmental player. Even then, he may spend many games as an inactive player. 3 WR's targets is plenty, given that we have top targets at TE and WR. This position seems to fit Thornton, who is a lock for the 53.
WR #5 (if there is one) is a gadget player or player who plays another position (e.g. returner, key STer, #5 RB). He would be active primarily because of his non-WR skills. We had Gunner last year. We could have Montgomery this year. Montgomery would replace Bolden as a STer.
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While I might spend $4M for a backup, I don't think that Belichick will. I think that there are basically two tiers of WR's.
Tier One consists of our top 3 WR's. We have 4. IMO, if all are healthy, then we trade one. So, for me, Myers may be the #4 best WR, but that isn't a roster position, and even more unlikely at $4M for a player who doesn't play ST's.