With a minute left to half-time in last week's match between Paris Saint-Germain and Barcelona in the Champions League, Lionel Messi pulled up suddenly.

He began nursing the back of his right leg. Play continued around him. He hardly moved, basically passing time until the half-time whistle sounded.

Twitter clogged up with messages pondering his health. He was duly substituted at the break for Cesc Fabregas. News filtered through that he had damaged his hamstring.

After the game finished 2-2, cameras from a Spanish television station followed Messi on to Barcelona's team bus. Back in the studio, analysts dissected his movements. "Look," said one of them, "it seems more serious here." Never before, perhaps, had so many people, including a sizeable chunk of Barcelona's 300 million fans, been so distressed over a strained muscle. Without Messi in the side, the team's leading scorer in the Champions League is Jordi Alba, a defender.

"Good result but a huge cost," screamed the headline the following morning across the front page of Sport, one of Barcelona's daily sports newspapers. Messi might be out for three weeks, it was claimed. News reports confirmed he would miss Saturday's league tie against Mallorca, but a tweet from Messi calmed nerves in the Catalan city: "I'll be back soon; luckily, it's not too serious."

He may yet play tonight in the second leg against PSG at the Camp Nou. He has proved remarkably resilient over the last few years. It wasn't always so.

The last serious injury Messi sustained was in a league match at the Vicente Calderon stadium against Atletico Madrid in September 2010. Tomas Ujfalusi hacked him down in injury time. It was an ugly scythe. The Czech defender got a red card. Messi hobbled off with a damaged ankle. He missed 10 days of training, his longest spell on the sidelines since the summer of 2008 when Pep Guardiola took over as manager at Barca, a remarkable run without serious injury given he is the most marked man in football.

Guardiola took the little Argentine aside early on and told him that he was going to build his side around him, converting him from a winger into a "false nine". He said he'd score three or four goals a game under him. He wasn't lying.

In Frank Rijkaard's last season in charge at Barca, Messi scored 16 goals. The returns over the following four seasons under Guardiola went steadily skywards: 38 (2008-09); 47 (2009-10); 53 (2010-11); and 73 (2011-12). This season, he's set to surpass last year's haul. Before missing the game at the weekend, he'd scored in 19 consecutive league games, at least a goal each against every team in La Liga.

Before the arrival of Guardiola, no- one doubted Messi's skill. What was in question, however, was his fitness. In each of the preceding three seasons, he'd missed at least 10 games through injury. He was plagued with repetitive muscle strains – hamstrings and thigh injuries, chiefly, and a broken metatarsal in a foot at the end of the 2006-07 season.

Things came to a head when he tore a thigh muscle against Celtic at the Camp Nou in March 2008 in the last 16 of the Champions League. Barca had won the first leg 3-2 in Glasgow, and an early goal by Xavi in the return encounter closed the tie out 4-2 on aggregate. Messi left the action in tears of frustration. He had only recently returned after a six-week lay-off in January and February. It was a recurrence of the same injury.

Guardiola took the helm a few months later. An individualised training regime was established for Messi, with a premium on correct stretching exercises, and advice on sleep and diet.

Messi thrived. Four Ballons d'Or followed. He scored goals in both of Barcelona's triumphant Champions League final wins against Manchester United in 2009 and 2011. It was noticeable that while his team-mates partied on the return flight to Barcelona from London after the 2011 Wembley final, Messi relaxed playing football on a games console. He may have been playing himself playing football.

Barcelona is not without a Plan B in his absence. On Saturday night, out-of-sorts Fabregas, playing in his position, scored a hat trick in a 5-0 demolition of bottom-placed Mallorca, but the club's fans would prefer to be able to call on his bionic powers to ensure safe passage into their sixth straight Champions League semi-final.