A 4-0 victory over Real Sociedad sent Atletico three points clear at the top of the league, with previous leaders Barcelona having lost at home to Valencia on Saturday.
And Diego - who moved to the Spanish capital on a loan deal from Wolfsburg in January, having previously enjoyed a loan spell at the club in 2011-12 - feels such success has been a long time coming.
"It was about time this team grew and won," he said. "When I first came here (2011), it was a very well organised team.
"Now we’re more accustomed to playing at this level, to winning.
"This is one of the strongest teams in Europe and I want to help the team keep winning."
And the Brazilian midfielder, who scored in the victory over Sociedad, was full of praise for coach Diego Simeone.
"My relationship with Simeone is spectacular," he continued. "He’s the best coach I’ve worked with in my life and has helped me a lot as a player and as a person.
"The trust he has in me certainly makes a difference in the decisions I make.
"It was great to start with a win (on Sunday).
"It was a very difficult and important game but I got a spectacular reception and was able to make a goal.
"I prepared a lot for this but I have to thank everyone - my teammates, the fans, the board and the trust of my coach. I’m very happy."
