Against KC, Butler played the left boundary almost exclusively, and Gilmore played the right boundary almost exclusively. When Rowe came on as the nickel, he played mostly slot, but all three got moved around a bit.
Against NOL, Gilmore primarily played the left boundary, Rowe started at right boundary. When Butler came in, it appeared that he primarily played the right boundary, while Rowe moved to the slot.
In 2016, through the Week-8 BYE, BB and Patricia tinkered a lot with the CB rotation involving the right boundary and the slot. Rowe, Ryan and Coleman were all part of that. In the early part of the season, Ryan played primarily the right boundary while Coleman came in to cover the slot in the nickel. Once Rowe got over his early-season ankle issues and began to pick up the defense, his role expanded, and the tinkering became more about Rowe and Ryan.
Some games Ryan would start on the right boundary and switch to slot when Rowe came in to cover the right boundary, and some games it was exactly the reverse, with Rowe moving from the right boundary to the slot when Ryan came in. Some games Rowe would play the right boundary primarily while Ryan came in to man the slot directly. By week-10, Rowe had completely replaced Coleman in the rotation, although the role-switching between Rowe and Ryan continued for most of the rest of the season with Cy Jones being included in the right boundary/slot rotations in a couple of games toward the very end of the regular season.
Through all of this tinkering in 2016 (and in 2015), Butler was almost exclusively playing the left boundary (and the left boundary was being played almost exclusively by Butler), though there were a couple of games when Butler followed a specific receiver almost regardless where the receiver lined up. And there were also a couple of games when Butler played some slot snaps regardless which receiver was lined up there. However, Butler almost never lined up to play the right boundary.
Gilmore has had significant past experience playing both boundary positions, as well as some slot.
From the time he began with the Pats last season, Rowe seemed pretty natural on the right boundary. AFAIK, he hasn't played much on the left boundary.
Butler's previous experience, AFAIK, has been almost exclusively playing the left boundary.
The fact that Butler was playing so much on the right boundary against NOL is significant, but I very strongly doubt that it's any kind of "demotion." I believe it's an attempt to make Butler - and, thus, the entire secondary - more versatile.
When BB was asked about Butler, he said, “Look, we’re into a new season, so I don’t think anybody’s performance this season is really where it needs to be or where it will be, ...” In Twitterworld this has been translated to, "... made it clear that the Patriots are not happy with Malcolm Butler."
For a CB, attempting to play the right boundary, after having spent years practicing the techniques and playing the left boundary, is very difficult - at least as difficult as a CB attempting to learn how to play press-man after having played zone-read exclusively for his entire career. To switch sides, the CB needs to take all his ingrained techniques and natural instincts and play a mirror version of them (that works both ways, too). More CBs fail in the attempt than succeed. Some CBs manage to adapt very quickly. More often, it's a process that simply takes time and reps.
So, my interpretation of BB's comment about Butler is just that he's not there - yet. However, if Butler continues to work at it and succeeds, by the end of the season, this secondary is likely to be downright scary for opposing offenses. OCs will have no effing clue which DB will be covering which offensive player from play-to-play. The secondary will have become nearly "positionless."
Chess to checkers.
. Really? I mean REALLY guys?!!! 
