When he got to the dressing room, a message from Paul Mariner awaited the young Ipswich Town player.
"Sitting on my seat was a telegram from Paul ... saying 'Just play your normal game. Good luck,'" recalled Yallop, now coach of the San Jose Earthquakes.
"I've still got the telegram, which was pretty special coming from an England international and a legend at Ipswich."
Today, the 59-year-old Mariner is head coach and director of soccer operations at Toronto FC. And he's still looking out for young players.
Mariner is 1-1-3 since taking over from Aron Winter after a disastrous 1-9-0 start. Toronto (2-10-3) plays at FC Dallas (3-9-5) on Wednesday in a battle of conference cellar-dwellers. Toronto FC will be looking to take points from a Texas side that is winless in 12 games (0-8-4) in all competitions since an April 14 victory over Montreal.
Toronto is the latest stop of a soccer career that has taken Mariner from Australia to North America.
Along the way, he has scored goals and soaked up experience.
At Ipswich he learned under the late, legendary Sir Bobby Robson, who used to call him Nipper as a father would a son. Robson bought Mariner from Plymouth Argyle in 1976 for 220,000 pounds.
Mariner said Robson's genius was surrounding himself with good people and knowing how to get the best of his players.
"He was a great man-manager," he said. "He would engage the core group of players. He would always ask them their opinions — whether he took note of their opinions is open for debate, but just to be engaged by such a great man."
Robson also looked out for his players. Mariner, who grew up in Lancashire in northern England, remembers how his manager would think of him whenever Ipswich played at Manchester United or City, Liverpool or Everton.
"He'd say 'Nipper, is your mum or dad coming?' I'd say yeah and he'd say 'well there's a couple of directors' box tickets.' That's like the royal box for working-class people like my mother and father.
"He'd always say 'Make sure you give them a wave when you score.' That sort of gives you motivation: A to play for him and B to score and wave to your mum and dad. It may not sound much, but in those days it was a massive gesture."
Since taking over from Winter, Mariner has listened to his players. Dress codes have been eased, formal team meals reduced and players have been given more freedom.
The arrest of Miguel Aceval, Luis Silva and Nick Soolsma for public intoxication while on a road trip in Houston was ill-timed payback to that easing of the rules.
Mariner seems to have elicited a better response from other players, who welcome the fact he has simplified their approach to the game as opposed to Winter's more complex system.
They also appreciate his emotion.
Mariner is hard to miss on the Toronto sidelines, pacing like a caged animal. His body language would do a silent film star proud, with every grimace or arm movement speaking volumes.
"You can't say he's not involved in the game," said striker Danny Koevermans. "I think if you asked him he would rather get some cleats on and go on the pitch to be the 12th man."
"He's a great coach to work with," he added.
Koevermans has scored seven goals in his last six games and was just named MLS player of the week. Mariner, no stranger to putting balls in the back of the net, has made a point of telling reporters just how good some of those finishes have been.
He clearly just appreciates good football.
Toronto defender Jeremy Hall, who has worked under similarly expressive coaches in Sasho Cirovski (University of Maryland) and John Spencer (Portland Timbers), welcomes a leader who wears his heart on his sleeve.
"You need those coaches. No disrespect to Aron, he's a great guy but he's just very soft-spoken. Paul does a great job of getting everyone fired up before the game. We get in a huddle in here (in the locker-room), we fight for each other and I think you see that out on the field. Everybody is willing to get stuck in and just do the dirty work for each other.
"It feeds off from the energy on the sideline. He's all into the game for 90-plus minutes and so are we."
In reality, Mariner's been all in for some 40 years when it comes to soccer.
The former England international was a bona-fide star in England in stints with Plymouth Argyle, Ipswich Town, Arsenal and Portsmouth from 1973 to 1988.
He was at his height in Ipswich. It was there that he got his first England call-up, won the F.A. Cup and UEFA Cup and was runner-up in the league.
"I think I probably played my best football there," he said. "I was still going strong when I went to Arsenal but injuries sort of clipped me back a little bit there."
But his career has been equally interesting since then.
He went on to play in Australia, Malta and New Zealand. While playing for a team in Auckland, he did commentary work for New Zealand television on the 1986 World Cup.
Four years earlier, he scored for England in a 3-1 win over France at the World Cup.
"I was absolutely on my knees," he recalled. "We played a really high-tempo game in a bowl of a stadium in Bilbao. I was really on my last legs. I just tucked it away."
The goal helped him equal Jimmy Greaves' consecutive game goal-scoring record for England.
"I'm proud to be associated with what I've done in the past," Mariner said. "But I very very rarely talk about the past. I never talk about the past with players. I always talk about the present or the future."
Yallop recalls Mariner as a big presence in the dressing room and an aggressive centre-forward on the field.
"I got to watch him for three years ... and Ipswich was at the top of their game at the time," Yallop said. "So I saw a lot of games with Paul and I thought he was fantastic."
Craig Forrest arrived as a young goalie at Ipswich just as Mariner was moving on. But he got to knew Mariner and knew all about his legend.
"Anybody associated with the club, even modern-day, all know the name of Paul Mariner," Forrest said.
If you wanted to document Mariner's travels on a map, you'd need a lot of pushpins.
"It's funny, you know," he said. "Because in those days, you didn't earn quite as much as the players do know. I had no idea what I was going to do. I wanted to keep playing as long as I could ... And I just started slumming around a little bit. Doing odd things. Then slowly but surely I sort of started getting into coaching."
He ended up in the sports agency business after starting up the First Artist sports agency with Jon Smith, a millionaire Arsenal supporter who had just sold his music business.
"He said to me 'What are you going to do, Paul?' I said I don't know. He said 'Well why don't you put your contacts in and I'll put my money in and we'll form a company.'"
Their first two deals were to become the European agent for Diego Maradona and to serve as agent for the England national team's endorsements.
It was a ground-breaking venture. In a 2008 interview with England's Growing Business, Smith recalled getting players to do their laces up on when coming on as a substitute to ensure the boot manufacturers got their time on camera. Not to mention persuading players to celebrate goals in front of certain advertisements.
Representing Maradona was "extremely interesting, to say the least," Mariner recalled. "A very quick learning curve."
While working weekdays for the agency, he commuted to Malta to play for a pro team there. He'd leave Friday, play Saturday in Malta and return Sunday to England for another week at the office.
"It was a bit of a tough go but you've got to pay the bills," he said.
He spent the better part of a decade in and out of Japan where he partnered with American Tom Byer in developing young players using a system developed by late Dutch coach Wiel Coerver.
Fate has played a large part in Mariner's life.
He was at England's Bisham Abbey National Sports Centre in the late '80s when he was approached about playing for the Albany Capitals of the American Soccer League.
Mariner ended up as an assistant coach at Harvard with John Kerr (now head coach at Duke). Kerr and Mariner had met at Portsmouth and become friends. Years later, Kerr invited him up to Boston and Mariner coached in the Ivy League and ran Kerr's local soccer club.
A year later in 2004, former Liverpool defender Steve Nicol asked him to become his assistant at the New England Revolution. They spent five years working together with the MLS side.
"I had a fantastic time. I learned so much from Steven. ... I'm just sorry we didn't win an MLS Cup. We got there three times (2005, '06, '07) but we just couldn't pull it off. So that's one disappointment.
"But we won the U.S. Open Cup and we won the Super Liga."
Mariner joined Toronto FC in January 2011 as director of player development when Winter took over. He says coaching was the last thing on his mind at the time.
"I took to my job like a duck to water. I really enjoyed getting involved with the player development side."
The job involved helping young players on and off the pitch. For those academy players who did not sign with the first team, Mariner would try to secure college scholarships.
He also enjoyed scouting and his contacts have paid off. He spied fullback Richard Eckersley at Plymouth Argyle during a brief managerial stint there and found Reggie Lambe thanks to New England's ties with Bermuda.
Back on the sidelines, Mariner says he is able to turn off the emotion of the game at the final whistle.
"I'm like a 500 Norton (motorcycle). I'm going at 120 miles per hour when the game's going on. But as soon as the referee blows his final whistle, it's as though my engine just turns off and I just go right back to relaxing.
"Well I'm a Gemini, so I'm probably a split personality anyhow. But I just seem to have that ability to just calm down immediately."
Mariner, who does not shy away from crediting others, also points to Nicol for teaching him about staying on an even keel as a coach.
"He used to say 'Never get too high, never get too low in this game. Because it will always find a way of hurting you.'"