England's coaches were alerted to Fikayo Tomori after shackling Marcus Rashford while he was captain for Canada's under-20s

The fact Fikayo Tomori first played for Canada rather than England remains a mystery to the coaches who handed him his international debut.

The 21-year-old Chelsea centre-back, who was born in Calgary and is also eligible for Nigeria through his parents, could make his senior England debut against Bulgaria on Monday.

But it wasn't until he shackled Marcus Rashford playing against England in an under-20s game three years ago that he alerted English coaches to his potential.

At the time, 18-year-old Rashford was hot property. A week before the game at Doncaster's Keepmoat Stadium in March 2016, he scored the winner in the Manchester derby and the previous month scored twice on his Premier League debut against Arsenal.

But against Tomori, who had been schooled at Chelsea after moving to England as a toddler, Rashford remained goalless - his only England debut where he failed to find the net - and Canada won 2-1.

After that display, England realised their oversight and Tomori never played for Canada again. An Under-20 World Cup winner's medal soon followed with England, but the reason he was even playing international football on that grey day in South Yorkshire was down to former Canada under-20s coach Rob Gale.

Five months earlier, he handed the-then 18-year-old Tomori an international debut to remember, more than 5,000 miles away in Mexico City. No wonder a game against an in-form Manchester United striker forward was straightforward in comparison.

"At the time, it was a mystery to Chelsea's youth coach Joe Edwards [now the club's first-team coach] that he had been overlooked by England," says Gale, who likens Tomori to former England and Nottingham Forest defender Des Walker.

"Joe welcomed the fact that me and my colleagues at the Canadian Soccer Association had looked into it and after telling him about what we could offer, we eventually brought him over to our camp in Mexico for two games.

"Fikayo felt it would be a good first taste of international football."

It proved a prescient judgement.

"The games were at altitude, the temperature in November was 25C to 30C, and Mexico are a powerhouse of our football region," says Gale, who now coaches Winnipeg-based team Valour FC.

"Fikayo flew into Mexico City at about 11pm, having travelled all day, and over supper we had our first face-to-face meeting.

"He had four days to get over his jet-lag, and then he made his international debut. Although he played a little safe, he did well, and we were unlucky to lose the game 2-1 having had a man sent off early on.

"But in the second game, we ended up drawing 1-1, with Fikayo scoring that day so it was a great little camp for him.

"Straight away you could see he was eager to learn, had a great self-awareness and was a very level-headed kid.

"I did find it strange that he hadn't been looked at at any age group with England, but straight away you could see he was eager to learn, had a great self-awareness and was a very level-headed kid."

Tomori's debt to Lampard and breaking Costa's nose

Tomori (left) was in the England team which won the Under-20 World Cup in 2017

Although Tomori was relatively slow to come into view, having also spent loan spells at Brighton and Hull City, his breakthrough came in another loan spell, at Derby County last season, where he benefited from regular starts in central defence.

Under the tutelage of now Chelsea head coach Frank Lampard, the 21-year-old was voted player of year and helped Derby reach the Championship play-off final at Wembley.

He also began to use his "incredible speed" according to former Hull team-mate Michael Dawson and showed his desire for "proper defending" by leading the division for tackles made by central defenders.

Lampard, who told Tomori about his England call-up after the Champions League win over Lille, describes the youngster as his "project" player and has praised his work ethic. "Every day, he is nailed on," the manager says.

That might also include a training ground incident while still at school where Tomori accidentally broke former Chelsea striker Diego Costa's nose and lived to tell the tale.

Since then, he has played every game following his full debut in the 2-2 draw with Sheffield United on 31 August, seemingly justifying Lampard's decision to let David Luiz join Arsenal in the transfer window.

Speaking at his first England press conference last week, Tomori said he owed Lampard "a great deal" for placing faith in him, much as England and Chelsea team-mates Tammy Abraham and Mason Mount have also benefited from the Lampard's support.

But the defender comes across as a slightly different character to his team-mates after saying he was just as likely to continue his Open University studies for a business management degree while away on England duty as he is to join his pals in their room playing Fortnite or Fifa on a games console.

"Football is not going to go on forever," Tomori said. "Whenever I retire, or if I get an injury I have something I'm working towards that can stand me in good stead for the future. I spend about eight to 10 hours a week, reading all the time, trying to learn new things."

Academy players Fikayo Tomori (left) and Tammy Abraham (right) have both broken into the Chelsea first team this season

A 'quiet' leader in the Des Walker mould

It was interesting to note that his current reading is about "leadership in business" for, while Lampard has spoken about how Tomori can be "quiet", Gale says he stepped up when he made him captain for the surprise 2-1 win over England back when he had Rashford in his pocket.

Prior to the game, Tomori used his knowledge of the England players to help settle the nerves of his team-mates, who were on average three years older than their Canadian opponents, according to Gale.

"Fikayo was saying, 'look I've played against these guys before, they are the same as you guys, just regular young lads, trying to make their trade so don't give them too much respect'," he says.

"It hasn't been the easiest road for him and he hasn't always been touted as the star man, but every challenge in front of him, he's risen to the occasion.

"He's a first-class person, first and foremost, he's humble and hardworking and if you're like that, you've got a chance to make it at the highest level, but he likes to defend and reminds me a little of Des Walker.

"He is a difficult defender to play against and you need that in the modern game. You see all these defenders now and half the time it's about what they can do on the ball, but we've lost the art of defending and that's what he's good at."

Dawson, who played with Walker at the start of his Nottingham Forest career, says he can see the likeness between the two defenders and says Tomori's pace and familiarity with team-mates will help him adapt to international football.

"It's a bit of a surprise how quickly he's made it into the England squad," Dawson says. "But he's taken his opportunity with Chelsea and Gareth is breeding a young group who play with no fear."

There has been little sign that life in the Premier League has fazed Tomori, who is in the top 10 for top speeds, interceptions and tackles among top-flight central defenders this season despite only playing five of Chelsea's eight games.

And after England's shaky display in the 2-1 defeat by Czech Republic on Friday, Tomori's arrival may be just what Southgate's team need.

If he makes his debut on Monday, there will be no sour grapes for Gale, who describes himself as an England fan. His only disappointment was with England's coaches, who did not approach him directly to say they wanted to recruit the youngster.

"It was a bit cloak-and-dagger, but I'm pleased his development has continued since that day," says Gale, who played for Fulham in his youth and is the brother-in-law of former under-17s manager John Peacock.

"At the time, what I knew was he would be very good for Canada, knew he was a great kid and knew he had ability because he was at Chelsea and I trusted the coaches there.

"We were happy to take that leap of faith, and we hoped he would like that experience and want to continue with us, which he did to be fair.

"He still stays in touch with myself and the national team manager to this day, so that speaks volumes of him."