The least surprising thing in any baseball season is the injury to Moises Alou. At 41, he’s one of the key hitters for the nominal best team in the league, coming off a season in which he hit .341. He’s also expected to miss the first four to six weeks of the season after undergoing hernia surgery last week. You would think the man is cursed.

Alou once missed an entire season after breaking his shoulder diving back into first base. He missed another after tearing up his knee on a treadmill. Having torn or broken nearly everything there is to tear or break, he’s lost the equivalent of at least another full season, and maybe a chance at the Hall of Fame.

During his career, Alou has averaged .303, with 28 home runs, 107 runs batted in, 35 doubles, 62 walks, and 75 strikeouts every 162 games. Chicago Cubs Hall of Famer Billy Williams, another left fielder with a hammering line-drive stroke, averaged .290 with 28 home runs, 96 RBIs, 28 doubles, 68 walks, and 68 strikeouts. The main difference between them is that Williams played every day for a decade. Taking the field counts.

While the exact nature of Alou’s latest malady was unforeseeable, though, the fact of it wasn’t. He hasn’t played 100 games since 2005, and no one thought he would this year. Bearing this in mind, it wouldn’t seem that the Mets need to do anything to replace him. If he misses the first six weeks and then plays as often as he has for the last several years, he’ll end up in about 80 games. That’s no more than what could have been expected.

Still, the news that the Mets’ left fielder was down immediately drew the attention of the baseball world to the fact that Barry Bonds, himself a pretty good left fielder, is still available on the free agent market. Alou and Bonds played the outfield together in Pittsburgh in 1990 and again in San Francisco in 2005 and 2006. Why not a third reunion?

The most obvious answer, of course, is that Bonds is 43, under federal indictment for lying about steroids, and the most notorious baseball villain since Pete Rose, if not Ty Cobb. Skeptics claim, in addition, that the Mets would forfeit their moral credibility and create a distracting circus if they hauled him in to take Alou’s spot in Shea Stadium. Neither of these arguments are very convincing. If Paul Lo Duca’s dalliances with no-neck bookies and Guillermo Mota’s steroid suspension didn’t unduly offend anyone, Bonds’s involvement in an absurd legal melodrama shouldn’t, either. And one hardly thinks that players like Pedro Martinez, who played in Boston for seven years, or Orlando Hernandez, who spent most of his career in a police state, are going to dissolve under the pressure of playing alongside the disgraced home run champion.

The far better answer is that the Mets don’t really need him, which is a simple thing to show. According to most projections, the Mets’ best lineup, including Alou, should score about 5.1 runs a game. Pencil in someone like Marlon Anderson or Detroit reserve Marcus Thames, in whom Omar Minaya is rumored to be interested, and that number drops all the way to 5.0. Pencil in Bonds for a line of .250 BA/.450 OBA/.550 SLG, and it might rise to 5.3, depending on where he bats in the lineup.

That sounds like a lot, but it really isn’t. Imagine three alternate timelines, in each of which the Mets played 162 games with their best lineup. In one, Alou plays every day and the team scores around 820 runs. In the second, Anderson or Thames play every day, and they score 800. In the third, Bonds plays every day and they score 860.

As this shows, if he played every day and if the alternative was 162 games of Marlon Anderson, Bonds would be worth 60 or so runs, which is an enormous amount, representing six games in the standings. In reality, of course, it would be more like 30 runs. Bonds himself will be only good for 100 or so games in the National League, and the alternative is not 162 games of a backup, but 80 of Alou and 80 of Anderson, Endy Chavez, and others.

For a team like the Tampa Bay Rays, who could play Bonds every day at designated hitter and compete in a much tougher division (and, unlike the Mets, can’t draw flies to the yard), three wins might well make the difference between a playoff chance and none. It would make good sense for them to put up with the Bonds freak show. The Mets, though, are more than three games better than any other team in the league. If the pennant race is really close, it will be because more has gone wrong than even having 100 games of Bonds could make up for. Given that, you can’t blame the team at all for scoffing at the idea of signing the crooked slugger. The math of his on-base percentage would indeed work beautifully in the lineup, but not quite well enough to be worth the bother.

tmarchman@nysun.com