I'm not going to lie, I'm writing this in a state that is inadvisable for writing. As Virginia Woolf illustrates in her essay about writing called "A Room of One's Own", there is a clear distinction between writing in the "red light of emotion" versus "the white light of truth" and that distinction does not advise the former. Well, after watching game after game without my current favorite player starting, I'll admit right off the bat, I'm freakin' pissed.
Here comes a player who has the talent and ability to make what has recently been a terrible offense not so terrible. The Giants know this, the fans know this, the experts know this, so why are they so intent on mishandling him? After his admittedly rough 10 at-bats in Arizona, which in his defense came against two really good pitchers and one above-average pitcher, we got an insight on Bochy's plan via Andrew Baggarly, "But Bochy reiterated that he will not yo-yo Belt in and out of the lineup. The talented first baseman will get every opportunity to settle in, the manager said."
Since then, here is a summary of everything he's done offensively: sat a game, came in via double switch in the third only to be taken out in the fifth (he went 0-1 with a walk), sat a game, sat a game, sat a game, started a game in which he accounted for two of the Giants' nine base runners, started a game against Roy Halladay in which he again got on base twice, sat a game to pinch hit a fly ball out, sat a game (presumably because the starter was a lefty) before pinch-hitting against a left-handed specialist, who posted a 13.95 K/9 against lefties last year, and still got a hit and the game winning run, sat a game (presumably because the starter was a lefty) before pinch-hitting against another left handed specialist who posted a 12.46 K/9 against lefties last year and proceeded to strike Belt out on three sliders, and sat today before pinch-hitting a bloop double to tie the game.
That seems like the dictionary definition of yo-yoing Belt in and out of the lineup and the complete opposite of giving him every opportunity to settle in.
Over that period, Belt is hitting .364/.500/.545 over 14 plate appearances, whereas Huff is hitting .158/.227/.316 over 22, not to mention Huff's terrible defense (in today's game, he committed an error at first, and then ruined a game-saving double play with a mental mistake while playing second base). For the season as a whole their numbers are also pretty incomparable as Huff's batting line of .182/.300/.333 is goes for a wRC+ of 75 i.e. 25% percent below average while Belt's .238/.360/.333 is surprisingly 12% above average. So why the hell is Huff starting over Belt?!
The first and most obvious answer is Bochy's long-established gritty veteran fetish. The second is the rumors that Belt is at odds with Giants' coaching staff about adjusting his stance to better protect an alleged hole in his swing. Apparently the Giants believe that Belt has a hole in his swing that gets exploited by inside fastballs and that this is the biggest reason for his alleged struggles.
Upon further analysis, this "hole" seems grossly overstated, as his heat maps reveal that there isn't really a statistically relevant hole on the inside of the plate. Now that is for all pitches—I can't find a heat map for fastballs exclusively (edit: actually Bay City Ball just published some heat maps that do exactly that)—but his pitch value data from FanGraphs shows that last year he actually hit fastballs pretty well. Above-average, in fact. (He may be below-average so far during 2012, but the sample size is irrelevantly small.)
Belt detractors claim that pitchers keep pounding the inside part of the plate with fastballs, but that is also not the case, as he's been getting fewer than 50 percent fastballs (as opposed to 58.2 percent last year, compared to the NL average of 56.8 percent). And he hasn't really been exploited by the inside fastball since Ian Kennedy and Daniel Hudson did so in Arizona.
The real trouble for Belt has always been breaking balls, as again FanGraphs' pitch value data shows. Bay City Ball posted an article late last year that talks about his problem with breaking pitches and features a very handy swing/miss (the pluses are misses) map against breaking pitches. Most of his whiffs against breaking pitches have been low and inside, which would give the impression that he was sitting on inside fastball and chasing the breaking pitches. People have always been getting on his case to hit the inside fastball, and perhaps this is the cause of his tendency to chase pitches down and in. In fact, the most recent example came in his last start, when his only swing-and-miss came against Roy Halladay, down 0-1 in the count, on a low-and-inside changeup.
It seems that because of this problem, Belt made the adjustment to move a little further up in the box and hit a little more aggressively in order to better hit breaking balls, which sounds by all measures of logic to be a good decision. Three games later, facing the nasty two-seamers of Kennedy and Hudson, apparently people had all the evidence they needed to say that Belt's methods weren't working and that he needed to adjust his swing. Ten at-bats are definitely not an ample sample size to make these kind of conclusions, but that hasn't stopped Bochy from relegating Belt to bench duties.
The more troubling thing is that even if Belt did in fact actually have this hole or some other problem that was causing him to struggle, how would relegating him to bench duties fix this? How is he supposed to adjust to big league pitching by sitting on the bench? The bottom line is that Belt is not playing to his potential because he hasn't gotten chance to settle in and adjust to big-league pitching, but even the uncomfortable Brandon Belt is still a better player than Aubrey Huff. As a result there's absolutely no reason Belt should be riding the pine.