Ok, I am going to start right out and admit this is a super optimistic take on Gay's impact with Sacramento. Most likely what I write doesn't come to pass and the Kings find themselves with a top 12 pick and the Cavs find themselves waiting and waiting and waiting to grab that 1st rounder; however, there is a scenario in which all the Negative Nancies of the opinion world have to eat their words on how bad/worthless this trade is for Sacramento.
First off I want to highlight that Sacramento has two very good, young players on its roster, and both are playing at high levels so far this year. DeMarcus cousins is having his best year scoring and rebounding and its not just because of his increased usage and (minor) increase in minutes. He has actually setting career highs in TS% and eFG%- which is nuts when you consider he has increased his usage dramatically to a league leading 34.9% (2.1 points higher than second place Westbrook). Isaiah Thomas has also seen a dramatic increase in usage, and a modest increase in minuets and has rewarded the Kings with increased efficiency and a big jump in his assist rate. In addition Thomas has excelled a the highly coveted skill of drawing fouls and earning FTs, despite playing fewer than 30 mpg he is tied for 19th for total FTs taken so far this year. The two players he is tied with have played 219 and 272 more minutes that he has.
If Cousins and Thomas are putting up PERs of 26.1 and 24.0 respectively, and generally passing the efficiency test, why are the Kings so bad at 5-13? More importantly why are they only 16th in Ortg despite two offensive studs? I am currently willing to chalk this up to two factors. First is that Cousins and Thomas play very few minutes for how good they are. Cousins has been putting up 30.8 per game and Thomas 28.2. Secondly, and relatedly, the rest of the team has been between poor and terrible on offense. None of the 5 players that they shipped out to land Williams and Gay were scoring even 10 ppg. Even if you add in all the players that they kept none of them are averaging 10 ppg. Part of this can be explained by Cousins' and Thomas' extremely high usage rates (#1 and #10 in the league) and part because there are no player outside of Cousins is averaging 30 mpg. On the flip side though none of these players is really earning quality minutes. Salmons, McLemore and Thornton- scoring guards all- were managing less than 10ppg on ~25 minutes each- and none of them were able to hit even 50% in TS. For comparisons sake Williams' disappointing tenure in Minny saw TS rates of 0.499, 0.513 and 0.526 and Gay's horrific shooting display so far this year was still better than Patterson, Thornton and Salmons to this point in the season.
So now things are very, very different in Sacramento. Williams has already played much better through 6 games than he ever did with Minnesota, and even if he regressed to those levels he would still be as good, or better than the players he is displacing, but I really want to talk about Gay, so here goes.
Rudy Gay has been terrible this year. He shoots badly, and to make up for it he does it a lot, as if he could hide his terrible shots in an ocean of terrible shots, so no one will notice them individually. Its not a good plan. Gay hasn't always been this bad though. Even though many mocked his contract, which was terrible, it isn't as if he never earned any off it, just that he wasn't a max player in a league built around max players. Prior to last season he was a high volume, moderate efficiency player, and he has improved his rebounding and assist percentages without skyrocketing his turnover percentages. Additionally he is only 27, this decline isn't likely to be physical and can be (potentially) reversible.
Gay has also already shown signs of pulling out of this dumpster fire of a season-plus. While he is shooting sub 39% for the season he has shot almost 42% over the last 9 games, which is much closer to his career average of 44% from the field. He has also slowly eased up on the trigger, attempting 16 shots per game over his last 7 games (right near his career average) rather than the 18.6 that he has averaged over the course of the season.
Of note for Gay from the Kings perspective is the fact that he is a minutes hog. Twice he has topped 3,000 in a season, and averaged more than 36 per game for his career. Usually a move that sends 4 players for 1 (essentially) would leave a team with a depth problem, but Gay's high totals will be replacing guys that are averaging 20-25 mpg.
Offensively with Thomas taking a lot of Vasquez's minutes and Gay and Williams replacing well below average offensive players with average (or, gasp, possibly above) play the Kings could go from a middling offensive team to a fringe top ten team as they come together.
Defensively there is little downside, and some upside. At 24th in the league in Drtg they don't have far to fall if the experiment of Gay/Williams as forwards on the court together doesn't work. In terms of improvement, Isaiah Thomas ranks significantly higher in ppp given up over the man he is replacing. Vasquez was grading out as the worst defender on the team by a wide margin. Williams and Gay are replacing a lot of average productivity minutes (at best) as well. In terms of conceptualizing the potential upside of the defensive trio of Cousins, Williams and Gay they each have very impressive wingspans of 7'5.75", 7'1.5" and 7'3". That is a lot of length in the front-court and can cause issues for opposing teams attacking the lane.
So here it is, best case scenario for the Kings. The length of Gay and Williams helps a mediocre defense out and also reduces the defensive load on Cousins. That lower defensive load leads to fewer fouls (he is picking up 5 per 36 minutes) and a lower offensive load as well thanks to Gay's and Thomas' usage allows him to play more than 30 mpg- replacing some low end bench play with high end starter play. Thomas proves to handle the extra minutes well and replaces mediocre offensive and terrible defensive play from Vasquez with all-star and passable efforts on those ends. Gay also returns to a non dumpster fire of himself, hitting shots at average efficiency and fighting back the urge to steal the ball from his teammates just to jack up one more shot, and replaces Patterson and Hayes' offensive (in both senses of the word) play.
Is this enough? Could the 9th or 10th best offense and 20th best defense combine to pull them out of a 5-13 start (including only 6 road games so far!) and drag them into almost playoff contention? Could the Cavs luck out and have the Kings end up with the 13th or 14th pick in a loaded draft due to a combination of improved play and lucky ping pong ball bounces? Who knows, but the possibility seems to exist where none existed last week.