MARTIN O'NEILL famously told a teenage David Marshall after his stunning display against Barcelona in the Nou Camp in 2004: "It can only be downhill for you from now on, son".
Neil Lennon has no intention of making a similar prediction for Tony Watt, the 18-year-old striker whose goal proved to be the winner against Barcelona last night.
The Hoops boss elected to keep the rising star on the bench for the start of the Champions League game, fearing the occasion might prove too much for a kid who has only 11 games' experience.
However, the decision to introduce his pace and power when Mikael Lustig injured his hip midway through the second half proved to be a masterstroke.
With eight minutes to go, the youngster latched onto an error by the very experienced Javier Mascherano, and wrote his name into the history books with a cool finish which belied his tender years.
Lennon revealed today that his own celebrations were muted – because he knew Barca would come roaring back.
He explained: "When Tony scored, all I was thinking was, 'It's not over.'
"Being me, I was also saying to myself, 'Surely they can't get three goals in the short time that's left?'
"You knew they would keep coming at us, and you could see the legs starting to tire and sense the hearts beat a little bit faster. But, thankfully, we saw it out."
Watt's goal was the clincher and made Lionel Messi's injury-time effort no more than a consolation.
Lennon could not hide his delight for the kid and said: "Tony only came on for 20 minutes or so, but caused them problems and got the goal.
"It was a brilliant, brilliant finish which showed great composure under the circumstances.
"It was fantastic moment for him. He scored a goal like that at Inverness, but this was a different thing altogether.
"Tony has been brilliant in the SPL, but I didn't want to start him last night because we knew Barca would have a lot of the game and that we might need his energy later on.
"Sami ran his heart out, and there was not much left on the bench, to tell the truth.
"But Tony scored a wonder goal and has written his name in the history books."
The loss of captain Scott Brown in the early hours of yesterday morning made picking the team and system to contain and ultimately beat Barca all the more challenging.
But Lennon – a rookie boss in the Champions League – rose to the occasion.
He said: "Scott picked up a sickness a diarrhoea virus on Tuesday night, and, at two o'clock in the morning he called the doctor.
"When I was contacted, my reaction was: 'Are there any more punches coming?'
"But you still have to believe. We have got a good squad here, and I have faith in them."
The tactics were duly tweaked, and the game plan adjusted. The result was THE result, and three more vital points to take Celtic to within two points of Barca at the top of Group G.
Lennon will review the entire match, as he does every game Celtic play.
But there is no doubt he will do so with a huge smile on his face, born from the fact the anxiety is over and the result is in the bag.
He revealed how he reached the decision to go with XI he did.
"Our thinking was that we could have gone with Beram Kayal in midfield," Lennon said.
"But you need to go that way if you have pace in wide areas, and we did not have that available to us last night with James Forrest out.
"So we decided to go with Miku and Sami up there.
"Miku did a brilliant job for us, in terms of trying to holding the ball up and linking up the play.
"Then defensively, we wanted to get him round their midfield guys.
"We wanted just to leave Sami up there, and do his bits and pieces as best he could.
"That was the thinking behind our formation, and the players we went with.
"You live and die by those sort of decisions, and we debated it long and hard all afternoon before the game."
The victory might have been even more clear cut, if a few key decisions had gone Celtic's way.
Lennon said: "I felt we should have had a penalty and Mascherano sent off before they scored. Tony was clean through, so how it was not a red card and a penalty I will never know.
"But, thankfully, in the end, it did not matter."