Earls has been handed the daunting prospect of replacing the talismanic Brian O'Driscoll, who will miss the entire tournament after undergoing shoulder surgery, in the No.13 shirt.
And the 24-year-old must step into some of biggest boots in world rugby only days after his partner Edel McGee gave birth to their baby girl, Ella-Maye.
But rather than be overawed by the demands of filling the void left by O'Driscoll's absence, O'Connell believes Earls will feed off the change to his home life.
"I've spoken to Keith and he's in good form," said O'Connell.
"I was lucky in that when we had our small fella I was injured at the time so I didn't have to go through what he's going through.
"It's a great time and he's in great form and is looking forward to joining up with the team.
"Having kids is great because it gives you a bit of perspective on life and rugby.
"We all take rugby very seriously and are a bit selfish at times, but it gives you perspective on how to treat games. Hopefully it will be a good thing for him.
"He's a lot more experience than in the past so hopefully I won't have to say a lot to him.
"He had a good World Cup and has been playing well for us. He was excellent against Northampton.
"Guys have to be trusted....we have to let him continue doing what he's picked for."
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