Salah was so bad in first training session Basel thought they had signed his twin but Keane knew Ronaldo would be world-class

Many believe Mohamed Salah is currently the best player in the world, something that would've seemed unthinkable when he was just a young man from Egypt struggling in training for Basel - and then when he was at Chelsea.

However, Salah was so bad in his first training session for the Swiss club that teammates and management thought they may have accidentally signed a twin brother!

It did eventually become clear why they made the signing in the coming days, though.

Then-manager Heiko Vogel said in an interview with Goal and SPOX: "Gegge Heit (Basel's sporting director) and I told him: 'Listen, just train as you like - we've already made our decision anyway'.

"Then he trained on the first day; everyone watched the session and we wondered if he might have a twin brother!

"The second day was a bit better, but not good. Gegge and I had already been talking him up for the tiniest things, saying stuff like: 'did you see that pass?'."

"And then came the third day," Vogel continued. "It was then that he destroyed everything, he was really unstoppable.

"[The first two days] he wasn't nervous. He was confident, but immersed in a new world. He had to acclimate himself in the truest sense of the word. He came to us from hot north Africa.

"It's always difficult when you get into an environment where you do not really understand the language. [But] I have rarely seen such a dominant appearance in two-on-five [on that third day]. It was absolutely extraordinary.

"He was so agile, so explosive. If he had the ball on his left foot, it was a goal. But Momo always had an eye for his teammates as well. After that performance everyone knew why we wanted to sign him."

It took Salah time to become the world beater we know him as now and Cristiano Ronaldo's journey has been similar, although he's been at the top for a significantly longer period.

His first three seasons at Manchester United saw plenty of positive signs but a lack of end product. However, his form exploded from the beginning of the 2006/07 season.

But former Red Devils teammate Roy Keane knew from the outset that the Portuguese had all the makings to be a special player.

Writing in his autobiography, The Second Half, Keane said: "I liked the lad straightaway. He had a nice presence about him, and a good attitude.

"What impressed me most was that he'd been given the option of staying in Lisbon for another year, on loan, but he said no; he'd come over to Manchester straightaway. I thought it was a good, brave decision - because he was only seventeen.

"After the first few days, watching him train, my reaction was, 'This lad is going to be one of the world's greatest players.' I didn't say it publicly, because I'd always be wary of building a player up too early - or knocking him down.

"He looked like a player. You have to look the part, and he did. [Zinedine] Zidane looked like a player - and Ronaldo looked like a player. The shape, the body language - they were there. A bit of arrogance, too. But he'd a nice way about him; he was very likeable.

"We forget that he was very heavily criticised when he first came on the scene. He was going down too quickly when tackled, his final product wasn't good enough. But - again - he was only 17, a kid. I was playing youth football for Rockmount, in Cork, at that age.

"He was amazing. He was immediately one of the hardest working players at United. Most of the players I knew worked hard, but Ronaldo had the talent on top of the work rate.

"He was good looking and he knew it. He was vain in that sense - at the mirror. He was a big lad, a big unit. I'd think, 'Good on yeh.' Looking at some of the other lads in front of the mirror, I'd think, 'Yeh f***in' nugget.'

"But Ronaldo had an innocence to him, and a niceness. I don't think he ever slackened off, or that he was ever more worried about the mirror than his game. I always felt that football was his love."

All eyes will be on Ronaldo and Salah on Sunday as Manchester United entertain Liverpool in the latest instalment of English football's biggest rivalry.

Expect the match to start off at a frenetic pace but all that matters is who has the last laugh.