Suffice to say that Beverley's season been a mixed bag at best, he's not as bad as some of his critics think but also nowhere as good as his supporters had hoped / claimed. here's a stat driven / observation supported analysis of what's happening, and what adjustment should be made.
First, the simple facts. Beverely is playing nearly twice as many minutes per game than last year, his effectiveness has been considerably reduced, but he has actually made some improvements to his game, and his overall effect is still fairly positive. I don't think it's a bad idea to keep starting him, but the some adjustments need to be made.
Perhaps the most glaring decline in Beverley's effectiveness is his 3 point shot, it came down from an above average .375 to a below average .333 one, though this part is actually the lesser of the concerns, he's taking more shots and the variance is well within expected flucation. If anything, he has made some improvements to his driving game, it's still bad, but it's getting better.
However, most of the following stats are far more worrisome .
(last year -> this yea)
Total Rebounding Rate : 8.7-> 6.8
Assist rate: 24.2 -> 10.9
Steal rate : 2.6 -> 2.0
Block rate : 2.2 -> 1.1
Unless you were kidding yourself, you understood that scoring was never going to be Beverley's strong suit, and that it would be the little things that keep him in the NBA, while little things are not entirely quantifiable by box scores, the 4 numbers described above is at least a general feeler for how much of little things a guy is doing, and obviously when comparing the same player, and you see a decline like this, you can reasonably conclude he's not doing those little things as well as before.
However, one needs to point out that the lineups with Beverley on the floor is still generally quite good, per 100 posession the team is +7.5 with him on the floor and only +1.8 without him, so he's obviously a net positive contributor for the most part. (granted, tonights turd sandwitch surely will take a chunk off that.)
So what's going on?
I think the very simple explaination is that he's simply playing too many minutes to be effective in his approach, I will cite a very easy number to reflect his, last year, per 36 min, he fouled 4.2 times, this year, 3.0 times, less fouls is good right? well maybe not when your an aggressive energy guy, it seems fairly evident that the role of a 30 min starter is making Beverley change his approach to become less aggressive, which plays very poorly against his strength, he's never going to be a guy that beat you with mad skillz or size / speed, he's good because he's aggressive and go all out when he's out there, but if he's no longer aggressive and going all out....
So the conclusion seems fairly obvious, scale his minutes back closer to 20 than 30 and let him be the energy guy who doen't care about trying to conserve energy to play 30+ . that Beverley was much more effective than this current one.
Would those minutes necceasrily go to Lin though? maybe not, Lin's playing 30min a game and giving him significantly more minutes is likely to have the same issue, the solution? play Aaron Brooks, he's been pretty darn effective, if inconsistent, but really for a 5th guard he's super over qualified at this point. sure, defensively he's very suspect, but by putting him in 10 min a game your likely to help get a more effective Beverley and maybe in Harden too (another guy that need some scaling back of minutes. though more out of health worries)
I would also like to point out that Beverley's abiltiy to navigate screens remains very suspect, he often doesn't seem to see it coming at all, the only thing worse than keep doding under the screen would be to be completely killed by the screen and let both the ball handler and roll man to go down the lane 5 on 4. Beverley does that a lot, he does kinda make up for it in other places, but a lot of defensive breakdown from the first unit starts when Beverley blows a pick.
This fanpost on the a Memphis fan site demonstrate multiple instance of such plays.
some of the example you see here, Beverley's failure to properly play the pick (or really even make a decision and stick with it.) cause some pretty bad break downs.
Screen reading can improve with experience no doubt, especially for guys who are committed to working on their defensive game, but currently, it's still very bad.
So essentially, they need to break Brooks into the rotation permenantly for at least 8-10min a game usually at the expense of Beverley's current minutes.