Walter Smith's unorthodox Man Utd training method transformed Cristiano Ronaldo

Former Everton, Rangers and Scotland boss Walter Smith passed away on Tuesday aged 73.

Smith was best known for his success at Ibrox, where he guided Glasgow giants Rangers to 10 Scottish league titles, five Scottish Cups, six Scottish League Cups and to the final of the UEFA Cup in 2008.

Yet he had a short but highly significant role as the assistant manager to Sir Alex Ferguson at Manchester United in the second half of the 2003/04 campaign.

This coincided with the first ever season of Cristiano Ronaldo at Old Trafford - the Portuguese winger had joined United the previous summer from Sporting Lisbon.

Ronaldo's transformation in his first season at United was remarkable; developing both physically and in terms of his playing style.

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Ferguson and Smith watch on during Cristiano Ronaldo training with Man United ( Image:

Manchester United via Getty Images)

Darren Fletcher - now in a coaching role at United - was a midfielder who was part of the first-team squad at the club that season.

The former Scotland international has previously recounted Smith's pivotal role in United's training that helped develop Ronaldo's game that season.

Smith had moved into the number two position at Old Trafford after the post had been vacated by Carlos Queiroz when he left the previous summer to take over as boss at Real Madrid.

Mike Phelan has been acting as assistant boss at Old Trafford since Queiroz's departure on an interim basis, but Smith stepped into the role from March until the end of the season - helping to oversee United's FA Cup triumph that year.

Quieroz - who had a close bond with Ronaldo - would return to United the following year but then-midfielder Fletcher has previously explained to beIN Sports the role that Smith played in his brief but influential stint at the club.

When asked who had the biggest impact on Ronaldo's quick change in development that season, Fletcher responded: "Walter Smith, when he joined as assistant manager.

"With Ronaldo, you could always see his talent and ability - it was obvious, and that is why the club had signed him based on that pre-season game when he tore us apart playing for Sporting Lisbon.

"He was a charismatic kid who had the ability and drive to become the best player in the world but he frustrated the life out of everybody.

"Everybody thought that if he could learn, it would take him up to the next level and then Walter Smith came in and decided not to give fouls in training.

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"It was a general rule, but I think the sole purpose was for Ronaldo.

"So Ronaldo would have been doing his skills and not passing the ball - which we wanted to eradicate - and the lads were fouling him.

"But Walter said that there would be no fouls and for two weeks, Ronaldo was tearing his hair out.

"He was going bananas because it was open season for fouling him."

The unorthodox method paid off for Ronaldo as he became one of the greatest players ever in the game, winning five Ballon d'Or titles across multiple successes with United, Real Madrid, Juventus and Portugal.