Two months after his arrival from Spartak Moscow, Vidic was introduced as an 83rd-minute substitute as United hammered Wigan at the Millennium Stadium in 2006.
It was the start of what has proved to be a medal-filled spell at Old Trafford for the popular Serb, who will sit out Wednesday's semi-final with Sunderland at Old Trafford after his red card at Chelsea on Sunday.
However, given Vidic's only other appearance in the competition that season was on his debut in the semi-final against Blackburn, and that was only for four minutes, the Serbia star felt there were others more deserving of the medal.
And given Rossi had started three matches earlier in the competition, and not even made the bench in Cardiff, Vidic opted to hand the medal over.
"I only played for a few minutes in the final and got the medal and, afterwards, even though it was a nice feeling and I felt part of the team, I gave my medal to Giuseppe Rossi because I felt it would be better to give it to someone who had played more minutes than me in the competition," Vidic told www.manutd.com.
"He deserved it."
The game itself though, won thanks to a brace from Wayne Rooney, plus goals from Louis Saha and Cristiano Ronaldo, was an important staging post towards the dominance United went on to enjoy for the next three title-winning seasons.
"We scored four and could have scored five or six," said Vidic.
"It was important to win that trophy because we hadn't won a trophy for nearly two years.
"After that, we started to win things again."