The Portuguese spent six years with the Premier League leaders, winning three league titles and the Champions League once, before leaving for Madrid in 2009.
“Cristiano is anxious; you want to start the game. He is in extraordinary physical condition,” Essien told a press conference.
The former Chelsea man also added that Jose Mourinho's side are prepared for encounter, while noting United's considerable attacking threat.
“In the Champions League it will be a different game. I'm ready and the team is as well," he continued.
“They have many attackers and it is up us to stop them.”