David Luiz said he left Chelsea to join Arsenal because of his “ambition” and to experience a “new challenge”.
The 32-year-old centre-half made his Gunners debut in Saturday’s 2-1 Premier League home win over Burnley after his move on transfer deadline day.
Chelsea, who beat Arsenal in the Europa League final, came third in the league last season with Arsenal fifth.
“I am a guy with ambition and that is why I moved. I like a new a challenge and new things in my life,” said Luiz.
“This is what gives me oxygen and gives me motivation and also to really enjoy this moment.
“I could have chosen a comfortable zone and got money and be cool and that is it.”
New Chelsea manager Frank Lampard told Luiz he would not be a guaranteed regular starter in his team and then allowed the Brazil international, who won six major honours in two spells at the club, to move across London to Emirates Stadium.