Alex Ferguson regrets not taking a more robust approach in Manchester United's UEFA Super Cup defeats to Lazio and Zenit.
United are back in the traditional European season curtain-raiser against Real Madrid in Skopje on Tuesday after winning the Europa League last term.
Champions League triumphs in 1999 and 2008 during their extended golden period under Ferguson also booked a place for United in the showpiece, although they were unable to add to the title they picked up in 1991 against Red Star Belgrade as Cup Winners' Cup holders.
The priority for United was to continue their dominance of the Premier League, meaning the scheduling of the fixture on a Friday in Monaco on both occasions did not sit well with Ferguson.
Nevertheless, Lazio's buoyant celebrations after Marcelo Salas gave the Serie A side victory in 1999 continues to irk the managerial great.
"To be honest with you, when we became successful I didn't used to view the Super Cup as the most important thing," Ferguson told MUTV.
"It used to be in Monaco on the Friday night and we had to go and play [in the Premier League] on the Monday, which meant we only had two days' preparation.
"So, in the games against Lazio and Zenit I played a lot of the younger players. I'm sorry I did that and I'll tell you why - because Lazio treated it like the World Cup final.
"They're dancing about the touchline and I was raging, saying I should have put the full lot out for the way they were celebrating."
Nevertheless, Ferguson feels his logic still holds despite lingering thoughts of what might have been.
"But the long-term view was always win your league. There's a lot of tribalism in the Premier League and I think if you ask the supporters whether they would rather win the league or the Super Cup, I know what the answer is," he added.
"So we viewed it a little differently and, in hindsight, I wish I'd have gone for it. At the end of the day, history is history and we could have won the Super Cup three times - if we'd played properly in Rome against Barcelona [the 2009 Champions League final defeat], maybe another one.
"I think it's one of these big regrets."