The four-time world player of the year hurt his left hamstring while playing for Barcelona on Nov. 10 and will be sidelined for 6-to-8 weeks, keeping him off the field until after Christmas.
"He's a kid who doesn't know how to manage himself because he is so passionate for the sport. Someone has to set limits for him," trainer Fernando Signorini, who has worked closely with Messi, told The Associated Press in a telephone interview.
"He's certain to have problems because of how he is. It's fine that you have a contract to play but the player also needs to know when to stop," Signorini said. "And since he cannot manage it, someone behind the scenes needs to understand that he needs to be managed."
Prior to his most recent injury, Messi said he was not yet 100 per cent recovered from the last one. But last week was the final chance to garner votes for this year's world player of the year award, so Messi played on in the hopes of winning a fifth straight Ballon d'Or.
Signorini, who also worked as Diego Maradona's personal trainer during the Argentine great's playing days, was Messi's trainer with Argentina but left the national team following Maradona's exit as coach. Signorini said Messi and Maradona share an obsessive passion for the game that clashes with unrealistic commitments put forth by their clubs and the international playing calendar.
For Messi, who has played nearly every game over the past five seasons, too many games may be taking their toll.
"He needs to have confidence in the people who are taking care of him, especially the people at Barcelona who are responsible for helping him reach the heights he has," Signorini said. "(But) the player also needs to know when to stop and take a break. He should know how to listen because he is such an intelligent person."
Messi, however, has said he would not set any limits to his playing time.
"As long as I feel well enough, I will play when necessary," Messi said in a report published in Argentine sports daily Ole. "I don't need to set limits. There's no need to look for things that don't exist. My plan is to play again when my body feels ready."
Fears of injury have increased since former Barcelona coach Pep Guardiola left the team after the 2011-12 season. An injury-free Messi helped Barcelona win 16 trophies since 2009, including four Spanish leagues and two Champions Leagues.
"Messi owes Guardiola a lot. His obsessive personality helped put order into Messi's life and it brought the best out of him," said Sebastian Fest, co-author "The Mystery of Messi" alongside former l'Equipe journalist Alexandre Juillard.
Messi, who had a history of injuries under previous coach Frank Rijkaard, saw his poor diet and off-field habits transformed, and his game improved. He also had physician Juan Brau assigned to travel with him fulltime, including when he played for Argentina.
"At first he (Guardiola) even tried to regulate Messi's playing time, to keep from playing so much, and that's when they started to butt heads," Fest said. "Messi told him, 'You don't understand, I have to play, always.' And when Guardiola didn't play him, he sometimes wouldn't show up for practice."
While Guardiola initially found common ground with Messi, by the end of the coach's tenure their relationship had soured to the point where the two are no longer on speaking terms, according to the book.
Messi missed the end of last season — and was hobbled during Barcelona's humiliating Champions League semifinal loss to Bayern Munich — because of injury, and appears to have taken little time to recover.
There have been problems off the field, too.
Messi has had to deal with tax fraud charges against him and his father Jorge, with the pair paying more than 5 million euros ($6.6 million) in back taxes. That dilemma and Messi's added anxiety of being healthy to captain a strong Argentina squad into the World Cup in neighbouring Brazil has made this season unlike any other.
But that, he said, hasn't changed him.
"I'm doing the same things I always have," Messi said. "This injury happened because it had to. I'm not the only person who plays so many games every season.
"I'm going to stick to the plan we set at the start of the season. There's no reason to do anything else."
Follow Paul Logothetis on Twitter @PaulLogoAP