The Premier League giants are believed to be close to buying the 27-year-old from Barcelona, with the Spain international's team-mate Gerard Pique letting slip the deal was all-but done.
Speaking to reporters on Thursday, Azpilicueta, who will play alongside the midfielder at the World Cup, praised the former Arsenal captain's talents.
"At the moment there's nothing official and he's a Barca player," he said.
"All I can say is what I already know about him. He's a great central midfielder with plenty of experience in the Premier League. The best players are always welcome at the best clubs.
"In my personal opinion, he's a special player.
"Few teams have this kind of player in their team, a central midfielder who gets forward really well and has great vision of the game, whilst there's also his statistics, which speak for themselves.
"He can adapt to various positions. Right now, we don’t have a player like Cesc at Chelsea."
Regarding his own form, right-back Azpilicueta - who played much of the season at left-back for Jose Mourinho - said he was happy to play wherever required by his club or the national team.
"I've played in various positions, that's true," he said.
"My natural position is right-back, although this year I've played on the other side. Whatever I can do to help the team, is best for me. I'm happy with how I've progressed."