Third base coaches and personal trainers do not have dissimilar roles in baseball. They serve and guide players.

Usually the third base coach holds the more perilous job. He makes instant decisions that often affect the outcome of games. When they make decisions that turn out to be right, people generally don’t notice. Their attention is focused on the runner who made the coach’s decision successful.

However, when the runner is out at the plate, fans – and others – blame the coach. George Steinbrenner, the Yankees’ owner, infamously did that in the 1980 playoff with Kansas City and stripped third base coach Mike Ferraro of his position for sending Willie Randolph home, where the Royals threw him out in a close game.

More recently, this week in fact, a third base coach, Dave Anderson of the Texas Rangers, burst into public view because he sent home Josh Hamilton, last year’s American League most valuable player, and Hamilton was not only out but he also broke his arm and will miss six to eight weeks.

Had Anderson done that for a Steinbrenner team, he would very likely have already been relieved of his duties. Steinbrenner never fired the Yankees’ trainer, Gene Monahan, who remains in that position 39 years after he began, one of the most remarkable runs in baseball history.

But when I talk about trainers, I don’t mean team trainers; I’m talking about players’ personal trainers, some of whom have gained notoriety in recent years. Two in particular stand out for their role in recent off-field baseball history.

One, Brian McNamee, has become noted as the trainer who said he injected Roger Clemens with illegal performance-enhancing drugs, contradicting the pitcher’s testimony before a Congressional panel and prompting a grand jury to indict Clemens on perjury charges, on which he is scheduled to stand trial in July.

The other personal trainer who has become infamous is Greg Anderson, whose refusal to testify in Barry Bonds’ trial saved Bonds’ rear end.

Bonds this week was convicted on a single count of obstruction of justice. The Federal jury in San Francisco was deadlocked on three counts of perjury against Bonds, and Judge Susan Illston declared a mistrial on those charges.

That combination of legal events strikes me as being incongruous. I am not a lawyer, and I did not hear the judge’s charge to the jury, but I don’t see how the jury could find that Bonds obstructed justice if it did not find that he lied to the grand jury. The outcome seems like a compromise among the jurors.

Again, I don’t have the formal legal background, but I would not be surprised if the judge threw out the conviction. On the other hand, based on the trial testimony I read I don’t see how the jury could have failed to convict on the perjury charges. Maybe you had to be there.

The trainer’s refusal to testify was critical because without it, Judge Illston did not allow the government to use evidence – an alleged Bonds’ steroids calendar, for example – without Anderson confirming it. No one has ever done a defendant a greater service than Anderson did for Bonds.

As long as the judge refuses to allow that evidence and Anderson refuses to testify, the government might as well drop the perjury charges.

As inconsistent as I see the jury’s position, getting back to Hamilton, I see a very consistent player. Consistency is an admirable trait in a player, but Hamilton’s type of consistency is not what anyone has in mind.

In 2007, after a four-year ban for violating baseball’s drug program, Hamilton missed a month with a sprained wrist.

In 2009, Hamilton was limited to 89 games by an assortment of injuries, including one caused by a collision with an outfield wall.

Last season another collision with an outfield wall broke two ribs and knocked Hamilton out for most of September.

Now the left-hand throwing Hamilton, who will turn 30 next month, is out of the lineup for six to eight weeks after breaking a bone in his upper right arm.

No one is suggesting that Hamilton is fragile or brittle. There are some players who are more prone to injuries than others. Ken Griffey Jr., for example, was at one time in his remarkable career viewed by many as the best player in the game, better than even Barry Bonds and more likely than Bonds to break the career home run record.

But then he encountered a series of injuries, many of them in collisions with outfield walls, and his career deteriorated.

Hamilton’s injuries have not undermined his career. In spite of the injury that nearly ended his season prematurely last year, Hamilton was named the American League most valuable player. The time he missed in September is usually critical in the m.v.p. voting, but Hamilton overcame his absence in the time the Rangers clinched the A.L. West championship.

His chances of repeating this year will depend on how the Rangers fare in his absence, where they are when he returns and what he and they do once he returns. By the time Hamilton is back in the lineup, the Rangers could be in command in the division race, they could be in a fierce fight with the Angels and/or the Athletics or they could be struggling.

More to the point at the moment, though, is the way Hamilton was hurt and his reaction to the incident.

Hamilton was injured trying to score from third base on a foul pop near third. He tagged up and ran at the urging of the Rangers’ third base coach, Anderson, who reacted to seeing the Tigers leave home plate uncovered when catcher Victor Martinez joined third baseman Brandon Inge in pursuit of the popup.

Hamilton, who later said he had been reluctant to run, nevertheless took off for the plate. Seeing that, Martinez retreated toward the plate, Inge hit him with a perfectly placed soft toss and Martinez tagged Hamilton as he slid by head-first. It was an unartful head-first slide, and Hamilton landed on his right shoulder. Hamilton called the play stupid – Anderson’s telling him to go – but it was his head-first slide that was stupid.

Hamilton, who two days later apologized to Anderson, said he slid head first because that was the only way he could have eluded Martinez. That turned out to be a bad instinct. His first instinct was better – not to run, though I think it was a good play, just poorly executed.

Some day players may come to understand that sliding head first is a low-reward, high-risk play, although as it turns out with Bonds there was higher reward and lower risk saying he thought what Anderson gave him was flaxseed oil and arthritic balm.