Martin O'Neill saw the best of Liam Miller from his time at Celtic when the young midfielder burst onto the European stage in the green and white jersey.
And the Ireland senior team manager, who honoured Liam's memory by selecting an Ireland/Celtic squad for yesterday's tribute match for Miller, admits that his move to Manchester United from Celtic caused "friction" between the two clubs.
And he also feels that Miller's career would have benefited from staying at Parkhead for a bit longer.
"He was there when I arrived at the club and was trying to break into the side, he finally made it, big time, really, in the Champions League matches, coming on as a sub against Anderlecht and then starting against Lyon, he did really well," said O'Neill.
"I was naturally disappointed to see him leave and join Manchester United.
"He was a really good footballer and I hoped he would stay at Celtic a wee bit longer, in retrospect maybe he should have done.
"He was learning his trade with us and he thought the move to Manchester United was something he wanted to do," added O'Neill, admitting that the lure of Old Trafford was hard to ignore.
"If Manchester United come calling, of course that's what you are going to want to do.
"Let's be fair, at Celtic at that particular time we had reached the UEFA Cup final, we were housing 60,000 people every week so I think Liam was just beginning to learn the professional game as much as anything else and he was doing well, doing well in an environment of good players like Mjallyby and Larsson so that was a great learning period for him.
"But he wanted to go to Manchester United, I wouldn't blame him for that, I just think perhaps if he had stayed with us a little bit longer he could have picked up the game, whereas as Manchester United he was competing against the likes of Paul Scholes, big players, and here within our environment players like John Hartson, Stiliyan Petrov and Henrik Larsson were helping greatly.
"But he had his own life to lead, this is what he wanted to do and while it caused a bit of friction between the two clubs for a while, that's what Liam wanted to do," added O'Neill,who was happy to lend his own support to the day out in support of Miller yesterday.
"To lose a young man in the prime of his life, a family man, those are the things that will stick most in our memories," the Ireland boss said, noting the presence of ex-Celtic players who had their own experience with cancer.
"I have the utmost regard for John Hartson and Stiliyan Petrov as people, but their battles were excruciatingly difficult and they showed great courage and determination to come back. That's the reason they are here today," he added.
"The turnout today shows the esteem he is held in."