Buy of the century? Why 'Little Pea' is a huge hit at United

It has been a year – and somehow, a short lifetime – since the announcement which led us to ask whether Manchester United were losing their minds as well as their grip on European football. The day after Bayern Munich's Arjen Robben had given last year's Old Trafford Champions League quarter-final second leg a distinctly gloomier complexion than Tuesday night's, United revealed the £6m acquisition of a young Mexican striker who, only 12 months earlier, had been contemplating giving up the game and returning to college education after struggling to make his way at his boyhood club Chivas de Guadalajara.

If it was a choreographed announcement, designed to prove that United could spend money to regain lost European pride, then your correspondent shared some of the scepticism. "A new signing who answers to the nickname of 'Little Pea' might not have the streets of Stretford humming with expectation in the aftermath of Champions League elimination," was my script from one year ago. Well, the streets were certainly humming after the 22-year-old's 18th goal in only his 20th Manchester United start against Chelsea on Tuesday prompted Jamie Redknapp's quite reasonable assertion that this is Sir Alex Ferguson's buy of the century.

Ryan Giggs was fairly happy, too. His eyes lit up in the depths of the Old Trafford stadium late on Tuesday when he described the way that Hernandez provides the supreme tactical advantage of creating pockets of space in front of opposing defences, as well as scoring all those goals. "He stretches teams," Giggs explained. "And that's great for the lads behind him because it gives them space to play. He has had a massive effect on the team because Wayne [Rooney] is able to pick up space behind him and [find] space to play and produce performances like tonight. He is really important for his goals – but not only his goals."

As Sir Alex Ferguson has observed, the most extraordinary part of this story was United's ability to quietly steal in and sign Hernandez. They had been trailing him since October 2009 and by 1 April of last year, his ability was public knowledge. Even The New York Times ran a feature on the forward headlined: "Hernandez could be Mexico's next big thing." The agents were circling but United had already concluded their business – knowing that a good World Cup for Hernandez could otherwise mean them losing out. United's head scout Jim Lawlor embarked on a three-week trip to Mexico, watched the striker perform for Chivas and Mexico, and a deal was struck under such cover of secrecy that only the player's father, Javier Snr, knew what was going on. "They told us they were going to Atlanta," the player's grandfather, Tomas, the first of three generations of father and son to have played in World Cups for Mexico, said recently. In fact, Hernandez and his father were in an Old Trafford executive box, watching the Bayern Munich tie.

Ferguson had been right to worry about events in South Africa. Hernandez scored twice and was clocked at 19.98mph, making him the fastest player in the tournament and United's players were immediately struck by what they saw. Ferguson thought Hernandez would need time – a season perhaps – but Paul Scholes thought differently. He saw Hernandez in pre-season training, caught the manager's eye and boldly declared: 25 goals. Giggs remembers that moment, too. "It seemed in pre-season that he was a born goalscorer; a similar scenario to Ole Gunnar Solskjaer, where he scores important goals and wants to score important goals," he said. The Independent's Lee Dixon was the first newspaper writer to observe what might be about to unfold. Spooling back the tapes of United's Community Shield win over Chelsea to prepare his BBC analysis, Dixon saw something.

"You could see the look on JT's face," Dixon wrote in this newspaper. "There were times when he was just hanging on, Hernandez was always trying to drag him out of position. The only reason Hernandez did not have a greater impact on the game was simply because he did not get the ball that much." We were witnessing a player with "the ability to be better than Ronaldo", Dixon wrote.

It was his temperament that raised doubts. Not in the way that Rooney's does but because Hernandez's upbringing, amid the bucolic delights of Guadalajara, is so far removed from a Croxteth boyhood – or from Federico Macheda's formative years in the poverty of Rome's rundown Ponte di Nona district. Hernandez simply has not known much struggle and after more than two years without a goal for Chivas, despite an ascetic lifestyle, he thought his football days were over. His father recalls a breakfast meeting at a restaurant between parents, son and agent, which was supposed to be a discussion on how best to move his football career on, turning into a counselling session. "He doubted himself; he doubted he was capable of playing in the first division," said Javier Snr.

Hernandez has sometimes been in too much of a rush – his former youth coach Professor Marco Fabian remembers him getting out of the car so quickly in his rush to get to training that he fell flat on his face – but in his only career crisis he put his faith in his parents. Ferguson considers them critical to his rapid adjustment. Three generations of footballers "gives a tradition to the family which he does not want to fail and pushes him to give his best", the manager said recently.

Hernandez certainly doesn't look like an individual wracked by inner doubts. La Sonrisa (the beaming smile) is a quality one Mexican publication was enthusing about only this week in its own analysis of why Hernandez has succeeded here. The Mexicans are also amused, incidentally, by the English struggling with pronunciation of "Chicharito" – the nickname behind his personal merchandise whirlwind. We saw the grin at its widest after the headed goal against Stoke City, which was well timed in more ways than one. It came only four days after Rooney had questioned whether United could still afford world-class players. Coincidentally, Hernandez commanded the cover of the United match programme the night Rooney went public with his doubts.

There are not too many complaints in the United commercial department, where Hernandez is concerned. The production run of "Chicharito" replica shirts last year was supposed to satisfy Mexican demand for a full year. They had sold out inside two months and United have recently overtaken Barcelona as Nike's most popular team in Mexico. The shirt production run will increase by 300 per cent this summer.

No one will blame Rooney for badgering Ferguson to play Hernandez on Saturday against Manchester City – a game which he, unlike Rooney, is very likely to start. Having scored nine of his 13 goals this season when Hernandez has been creating those pockets, Rooney knows his value. Manuel Lapuente, a former coach of the Mexican national team counselled this week against excessive expectations. "You have to leave him, let him grow, continue with these achievements and hope that these achievements keep continuing," he said. But Hernandez has come a long way in a year. He remains a young man in a tearing hurry.