With Sunday's clash coming just days after the birth of his first child, a girl Ella-Maye, Earls could seemingly be forgiven for having his mind elsewhere.
But O'Connell believes it'll be anything but, insisting Earls has been revitalised by the new addition.
"We all take rugby very seriously and are a bit selfish at times, but it (becoming a parent) gives you perspective on how to treat games. Hopefully it will be a good thing for him," he said.
"I've spoken to Keith and he's in good form. 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.
"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."