, it felt for a moment as though Leonardo da Vinci had mangled his painting hand just as he was about to apply the final brushstrokes to the Mona Lisa.
Imagine her unfinished, waiting forever for Leonardo to give her that pursed, so famously enigmatic smile. Equally gruesome would be if Messi falls just short of completing his own masterpiece — of setting a record for goals scored in a calendar year.
Messi has 84 for his club, Barcelona, and country, Argentina, in 2012, an otherworldly achievement but still not the record. That, for the next few days or weeks at least, belongs to Gerd Mueller, the Bayern Munich and Germany striker who was nicknamed "Der Bomber" for his stocky, power-lifter's build and explosive shots with both feet. In 1972, the same year he also lifted West Germany to victory over the Soviet Union with two goals in the final of the European Championship, Mueller scored 85 times in just 60 matches. Astounding.
That the record has stood for 40 years, untouched by successive generations of brilliant scorers such as Diego Maradona or Brazil's Ronaldo, is a measure of how special Mueller was and Messi is to get so close to breaking that mark.
So it made total sense that Barcelona coach Tito Vilanova brought on Messi for 30 minutes in the Champions League on Wednesday night, even though he really didn't need him.
With four wins in Group G, Barcelona could have lost this last game against Benfica and still have comfortably gone through to the knockout stage of the competition that begins in February.
As he did for Andres Iniesta, Xavi Hernandez and his other first-choice players who watched from their seats, Vilanova could have given Messi a rare night off, saved his most valuable star for more vital encounters and avoided the unnecessary risk of injuring him in a game of such little import that four of Barca's starting XI were B-team, not first team, players.
But Messi, football addict that he is, hates sitting out games. And, although he's only 25 and the best footballer of his generation, perhaps any generation, even Messi cannot be sure he will get this close again to Mueller's mark.
So, of course, he had to come on. He owed it to his sport as much as to himself. The buzz, cheers and applause from the Camp Nou crowd when Messi slapped hands with Rafinha, the 19-year-old B-teamer he replaced on 58 minutes, and ran onto the pitch, showed how thrilled his fans were at the prospect of witnessing Barcelona's all-time leading scorer write yet another page of football history.
The sickly hush and the way Vilanova chewed his thumbnail 28 minutes later told a story, too.
There are few grimmer sights in football than Messi being gingerly helped onto a stretcher and carted away. Not just because football would be poorer if it lost this treasure for any extended period of time but also because there's always that nagging concern with Messi, that he is only a bad tackle away from serious injury. Because of his slight build and because he's so quick and skillful, some lesser opponents have no other answer than to hack him down.
Like Luisao. Messi had been on the pitch for just 49 seconds when the Benfica captain and defender upended him with one of those calculated fouls cynical professional footballers do so well — chopping legs and then trying to shaking hands. Referee Svein Oddvar Moen from Norway knew better, whipping out a yellow card for the Brazilian.
Barca captain Carles Puyol, always so protective of Messi, gave Luisao a piece of his mind. But Messi, as is his wont, picked himself up without fuss. He needed growth hormones as a youngster to get to the 5-foot-5 (169 centimeters) he is now. He's generally smaller than the players who clatter into him but he doesn't give them the satisfaction of knowing they've stung.
Which is why it immediately seemed serious when Messi didn't get up after coming together with Benfica's goalkeeper, Artur, another Brazilian. Messi, to his credit, generally doesn't do the whole rigmarole of rolling around in agony like other players, including some of his teammates. So many feared the worst this time as he lay on the ground, hiding his face with gloved hands.
Messi grimaced on impact of running at speed into Artur with the ball at his feet. He could have gone down right there. Many other players would have. But Messi stayed upright, took a few more steps, swiveled and shot at goal with his aching left leg before collapsing in a heap. Even though he was hurting, he couldn't, wouldn't, waste a chance to score, to match Muller's record. As it turned out, Artur saved Messi's lob.
"I sincerely thought it was the last ball I would be touching for a long time because of the pain. I tried to go ahead and shoot but I didn't have the strength," Messi said.
Vilanova said he had no regrets and that it wasn't the Barca way to molly-coddle its superstar.
"He's a player that likes to play," he said. "He's not focused on breaking the record that everyone is talking about.
"If I had a do-over I'd make the same decision, seeing that he can get injured at any moment."
The diagnosis for Messi was reassuring: bone bruising to the outside of his left knee. Barca said he did gym work Thursday. Messi had injuries earlier in his Barca career, and was notably left out of the team that won the 2006 Champions League final because of a thigh injury. But more recently he has been remarkably durable — one reason why he has moved so close to Mueller's record. Barca said Messi hasn't missed a game with injury since September 2010, when Atletico Madrid defender Tomas Ujfalusi crunched his ankle in a tackle, damaging ligaments.
Messi has four more games in 2012 to overtake Mueller — or less if he doesn't recover for Barca's league trip Sunday night to Betis.
"It is not an obsession. If it happens, it will happen when it does," Messi said Thursday. "It would be nice to reach a record that has been there for such a long time. But it is not something that worries me. If I don't make it, no problem, but I am very close."
John Leicester is an international sports columnist for The Associated Press. Write to him at jleicester(at)ap.org or follow him at http://twitter.com/johnleicester