The weekend’s news from Spain will no doubt cause some nail-biting days and sleepless nights at AEG — the company that’s shelling out all those millions to bring David Beckham to America. Wouldn’t you know it — Beckham has gone and got himself injured while playing for Real Madrid on Sunday.

Beckham limped off in the second half in evident discomfort. It’s his right knee — damage to the internal lateral ligament say the initial reports. Fabio Capello, the Real coach, gave a decidedly nontechnical prognosis — “it could be something important — we will have to see” — and ruled Beckham out of tomorrow’s crucial European Champions’ League game against Bayern Munich in Germany.

Latest reports say Beckham will be out of action for a month. From AEG’s point of view, that’s not all bad news — a month in which no further injury can occur to upset his scheduled August arrival here! But the incident does underline just how precarious things can be in pro sports.

The injury came from a routine, done-it-a-thousand-times play — Beckham delivering one of his famous right-footed crosses. But this time something went wrong and the knee rebelled. That raises the sort of doubts that don’t bear thinking about when you’ve just made a multimillion-dollar investment in a player who is being hailed as the man to lead American soccer to the promised land.

Just how durable is Beckham? Is he, at the age of 31, beginning to show the fragility — to say nothing of the prolonged recovery periods — that afflict older players? His past record is good: He has not been an injury-prone player. He has had one serious injury: In 2002, he suffered a broken metatarsal bone in his left foot — that time it was the result of a violent tackle from an opponent. Beckham was hurried back in time to play for England in the World Cup six weeks later — his fitness was in doubt, but the pressure to have him participate with an English team that believed it could win the tournament (it was knocked out in the quarter-final stage by Brazil) was too great to resist.

When Beckham eventually comes here to play for the Los Angeles Galaxy (the club having hastened to assure all and sundry that it “does not expect this injury to affect his arrival”), he will be much in demand, not only for regular season games and exhibition games, but for time-consuming and draining publicity events. The temptation to overexploit him will be immense — so this weekend’s protest from a possibly overworked knee might well serve as a timely warning.

While Beckham is free of the injury-prone tag, the same cannot be said of Claudio Reyna of the Red Bulls, so far the only other expensive signing under MLS’s new “designated player” rule. Reyna’s seven-plus years playing at the top level in England’s premier league have been sprinkled with serious injuries, including a torn ACL when with Sunderland (that sidelined him for most of the 2002–03 season) and a broken ankle at Manchester City, which saw him miss nearly half of the 2004–05 season. Probably the most vivid recent image of Reyna in action was the incident in last year’s world cup, when Reyna had to quit the field after being injured in the first half of the loss to Ghana — the loss that knocked America out of the tournament.

Reyna suffers both the injuries and the accusation of being injuryprone with the same stoical calmness that marks his play on the field. Sure, there have been injuries, he says, but “I don’t like to really talk about this — some of them have been big, big mistakes by physios in England. Playing six games with a broken ankle when no one knew it didn’t help, nor did playing with a torn muscle that a doctor in Germany said was the biggest he’s seen in 20 years.”

Knees are certainly the most vulnerable part of the soccer player’s body. Another star knee in trouble this weekend was that of Manchester United’s Wayne Rooney, who also had to hobble off the field — “He’ll go for scan,” said coach Alec Ferguson, who was critical of the heavy tackle from Liverpool’s Jamie Carragher that caused the injury.

But it was Real Madrid that really suffered, getting a double dose of damaged knees. In the same game that saw Beckham limp off, forward Jose Antonio Reyes departed on a stretcher with suspected ligament damage to his left knee.

Player injuries are always something of a double-edged sword, depriving a team — and its fans — of a key player but at the same time opening up a chance for a younger replacement.

It is at that point that MLS feels the pinch, because bench strength has never been one of the league’s strongest features. Indeed, the whole idea of a team salary cap works against it, with the lion’s share of the money being logically funneled to players likely to be in the starting 11.

That circumstance should entail two priorities. First, the league should ensure that its referees clamp down hard on physical play. This is something to which MLS does pay attention. It has a refereeing “mission statement” that emphasizes the playing of “a safe, entertaining game … in which skillful attacking play is encouraged.” Sadly, that laudable intent gets lost too often on the field with referees being far too lenient with rough tacklers. MLS has developed — and its coaches seem proud to adopt — a reputation as a “physical” league.

The second priority is for the clubs to ensure players’ fitness. This one may have given us yet another example of just how canny a coach Bruce Arena can be. One of his first moves on taking over at the Red Bulls was to hire the former national team trainer Pierre Barrieu, enthusiastically welcomed by Arena as “superbly qualified to assist in preparing our players for competition.”