Atletico were criticised in some quarters for perceived negativity against Malaga but former Chelsea man Tiago thinks their work rate as a team has already improved since Simeone's arrival.
He told the official Atletico website: "It is true that we are working very hard and I think that it because we all feel important.
"Everyone believes they have a chance to play and this is very important for a team, to have a group of people that in any moment is ready to give their contribution."
Villarreal sit in the relegation zone after a terrible first half to the season, but Tiago also thinks that Atletico must concentrate on their performance if they are to win the game.
"More than looking at Villarreal, I think that at this moment we have to look at ourselves," Tiago said.
"We have to be united on the pitch because it won't be easy. Villarreal have great players but with the confidence and excitement that we have I think we are going to win."
Simeone has some problems in defence with Luis Perea and Alvaro Dominguez both suspended, but right-back Silvio is fit again after two months out.
Jose Molina's first game in charge of Villarreal also ended in a draw last weekend as his team surrendered a two-goal lead over Valencia.
However the performance was encouraging and the former Atletico player believes his new side can win away from home for the first time this season when they head to the Vicente Calderon.
"I am optimistic about Sunday because Villarreal tries to always have the ball, wherever we go," Molina said. "Despite our position in the table, when we go on to the field our philosophy doesn't change.
"I don't care how long it has been since we won away, the only thing that interests me is winning the game.
"We are going with the maximum motivation to play with great intensity. After that it is normal that the best team will win and we have to ensure that is us and we take the three points."
Leading scorer Marco Ruben misses out through suspension for Villarreal but midfielder Bruno is available after his fifth booking of the season against Valencia was rescinded.