The French full back made his long-awaited return to action as a second half substitute in our 1-0 semi-final second leg win away at Burton which sealed a 10-0 win on aggregate.
The Blues fielded a side blending youth and experience with teenager Ian Poveda making his debut and Felix Nmecha coming on as a second half replacement for his first taste of senior action.
And Mendy, who also looked razor sharp on his return to the fray, was full of praise for his young colleagues.
"It was not a bad performance, we had lots of young players. We said to them don't be shy, enjoy, and they did today,” said Mendy.
"It is not a strange game, we did a good part in the first leg and we came here to try and do the same. To play well and win the game.
"It was important to win the game. The conditions were not great but we prepared for this."
On his own return to action, Mendy added: "I feel good, the most important (thing) is my body feels good, my legs and I'm happy."