Mikel was arguably the most sceptical member of the Blues squad when interim manager Rafael Benitez first experimented with the move at the recent Club World Cup.
The player who has been Chelsea's anchorman for most of the last six years admitted his "shock" at lining up alongside Luiz in the semi-final against Monterrey.
Mikel even suggested his team-mate had reneged on an agreement for the Brazilian to play a holding role, going as far as to say: "I think he needs to play at the back."
Benitez clearly thinks otherwise, having started Luiz in midfield again in Chelsea's last two matches, to spectacular effect.
Several of Mikel's team-mates have applauded the move and, having returned from suspension to play Boxing Day's 1-0 win at Norwich alongside Luiz, it appeared less of a concern for the Nigerian ahead of Sunday's trip to Everton.
"It affects you because I've been here for a long time," said Mikel, who has become used to lining up with Frank Lampard or Ramires. "I've always played with Frank and now I've played with Rami as well - they're all great players. And now I have to play with David Luiz.
"It's just a lot. It's a lot, I think, psychologically as well. You think, 'If I'm playing today, who am I going to play with?' - because they're all great players.
"I've played with Frank for a long time and I've always enjoyed playing with Frank, and Rami as well, and [now] with David."