There is no way around it: Carlos Beltran’s season has been a disappointment so far.

The 28-year-old centerfielder, who signed a $119 million contract with the Mets over the offseason, is hitting .285 AVG/.342 OBA/.444 SLG – not much better than Cleveland rookie Grady Sizemore. While not bad at all, this is hardly what anyone was expecting after his long-awaited breakout season finally came in 2004 with the Royals and Astros.

Even a pessimist, figuring 2004 was probably the best year Beltran would ever have and that his numbers would be expected to decline in pitcher-friendly Shea Stadium, would have expected better.

What’s especially puzzling about all this is that the main reason Beltran was such a highly coveted free agent is his broad base of skills. When a player hits for good average, draws walks, hits for power, ranks among the best base runners in baseball history, and plays fine defense at an important position, the reasoning goes, he might see a decline in one aspect

of his game, but that should be offset by his excellence in other aspects. In 2005, however, the only area of Beltran’s game that hasn’t suffered is his batting average.

This, at least, is what the raw numbers say. The more interesting numbers, I think, are his home/road splits. In 83 road at-bats, Beltran has hit .325/.360/.566 with five home runs and five doubles, a performance more or less exactly in line with optimistic expectations. In 129 home at-bats, he’s hit .264/.326/.372 with two home runs and eight doubles, which is terrible.

Personally, I suspect that rather than injuring his thigh muscle during the Subway Series last month, Beltran aggravated a condition that’s been bothering him all year. This would explain his lack of steals and triples, his surprising lack of range in the field, and go some way towards explaining his lack of power, especially at home. A hitter generates force with his legs, after all, and you need to generate more force to hit a ball through the thick, smoggy air over the distant outfield walls at Shea.

Beltran’s home-away splits offer another interesting nugget of information: He has walked 13 times at home against only five times on the road. Along with the leg injury, the key to Beltran’s season-long funk may lie in that difference.

Any Mets fan who’s watched a fair number of games this year should be able to call up the image of Beltran at the plate. When I do that, the image is of a tentative and passive hitter, offering at pitches on the inner half of the plate on which he can easily turn, but letting others pass by. That’s the Beltran who hits at Shea – one without much power, who’s content to draw the free pass when he can, and is otherwise aiming to pull the ball down the line or peg it into the gaps. The Beltran who hits on the road is much more the sort of player everyone expected to show up at Shea this year: a disciplined but aggressive line-drive hitter with substantial power.

While I certainly didn’t have the foresight to predict this, Beltran’s performance thus far makes a good deal of sense. One of the most exciting things about his 2004 season was the huge increase in his walk rate. It’s something he worked on, training with a special hitting machine that shoots out tennis balls on which numbers are written. The balls come out at up to 150 miles an hour, and the point of the exercise is to read the numbers on the ball and improve your pitch recognition. Along with the improved plate discipline he showed last year, unsurprisingly, came increased home-run power, along with the side benefit of getting on base more.

What happens, though, to a hitter to whom pitch recognition is so important when that ability is taken away? I think we’re finding out with Beltran for a very simple reason: Shea probably has the worst visibility of any park in the majors. Anyone who’s paid good money for a field-level box will tell you as much. Theories vary – some people claim it’s swamp gas, while others say it’s the fault of the airport – but the fact is that down toward the field in Flushing, everything looks as if it’s being seen through a haze. Add in the fact that batters have long complained the batter’s eye in center field is inadequately blocked out, and you have an environment that does more than any other in the majors to make it difficult to see the ball.

Beltran’s increased walk rate and decreased power and average at home could easily be the result of his laying off more pitches and not connecting as solidly with the ones he hits.

That’s one theory, anyway; Beltran may also just have had 129 mediocre at-bats at Shea, which can happen even to the best players. Whatever the case, it’s almost certainly nothing that time and good health won’t take care of. Beltran is in the third month of what will be eight years with the Mets. Those months have been a disappointment, but there’s no real reason yet to think that he will be.