The Brazilian says los Rojiblancos can only focus on each game as it comes and maintains the belief they still have an opportunity to seize the league title.
Diego has called on his Atletico Madrid teammates to trust themselves and not think too far ahead as they look to continue their title bid.
Los Colchoneros took advantage of Barcelona's surprise 1-0 defeat at the hands of Valladolid, with David Villa scoring twice in a 2-0 win over Celta Vigo on Saturday to send his side above the Catalans into top spot.
Speaking to journalists after the game, Diego spoke of Atleti's need to retain its concentration for the rest of the campaign and focus on winning itself rather than simply hoping for Real Madrid and Barcelona to make errors.
'We know what we have to do," the 29-year-old told reporters. "We have to keep trusting. Every game has to be a final and we must take it game by game. We are focused on our game. It was a very complicated, very difficult encounter, so we did well."
Diego has played four times in La Liga and scored once since re-joining los Rojiblancos from Wolfsburg in January and expressed his satisfaction with his performances as well as the quality of his teammates, most notably Diego Costa.
"I'm feeling very well," he said. "I'm playing more and more minutes. Some things you can only get in games. In training I feel great - I think I'm going in the right direction.
"[Diego Costa] has indisputable quality. If we win with or without him, we know its importance, but if we don't have him available we have to find alternative solutions. We have a team of great quality with spectacular players. David Villa did very well."
Atleti sits top of La Liga with 64 points from 27 games, but is level with Real Madrid which have played a game less and takes on Levante on Sunday.