The 29-year-old has since become a key figure in Antonio Conte’s 3-4-3 system.
He has helped the Blues to the top of the Premier League table and has been named in the PFA Team of the Year.
David Luiz insists he knew his move back to Chelsea would be successful
And the Brazil international claims he was always positive his return to Stamford Bridge would go well.
"I’m a positive guy and I always imagine the best for me," Luiz told the London Evening Standard.
"I’m also realistic. When I came back I knew I was going to play in the most difficult League in the world.
"It was difficult for us at the beginning, but now we, not just me, are playing very well. It’s good to be in this way.
Chelsea line-up predicted to face Tottenham Hotspur in the FA Cup semi-final Thu, April 20, 2017
Express Sport predicts who will start for Chelsea in their FA Cup semi-final clash against Tottenham Hotspur at Wembley on Saturday (5.15pm)
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Who will Antonio Conte pick to start for Chelsea against Tottenham?
"Of course, I’m happy, but the season is not over.
"Football changes from one day to the next, so I keep my feet on the floor, stay grounded. I keep my humility.
"People ask me if this is the best form of my career. I don’t remember the past, I’m getting old! But I do think I’m playing very well.
"I’m older and have more experience. I am more mature and I am happy with this."