BARCELONA, Spain (AP) -- Atletico Madrid has a second chance to prove it can be considered a real contender for the Spanish league title when it visits high-flying Barcelona on Sunday.
Two weeks ago, Atletico flopped in its 2-0 loss at Real Madrid in the first serious test of its championship credentials.
Now Diego Simeone's side will have to find a way to slow down Barcelona's league-record start and forward Lionel Messi, who is looking to pad his single-year milestone of 88 goals in 2012.
"Simeone told us that we have a debt to pay for the game we played in the Bernabeu (against Madrid)," Atletico midfielder Gabi Fernandez said. "We didn't play the game we needed to against Madrid. We hope we can do so this time at Barcelona."
Third-place Madrid will host struggling Espanyol earlier on Sunday.
Unbeaten Barcelona has a six-point lead over Atletico and an 11-point lead over Madrid entering round 16.
The match at Camp Nou Stadium will feature the league's two leading scorers.
Messi has found the back of the net a competition-best 23 times through 15 games, while Atletico's Radamel Falcao scored five times last weekend to take his total to 16.
"We have been trying for 10 years to figure out (how to stop Messi), but it is tough because he is such a dangerous player once he has the ball," Gabi said. "The only way is to help one another and to play as a unit, trying to prevent him from being able to attack us one-on-one."
Barcelona has won the previous four meetings, with Atletico's last victory at Barcelona in the 2005-06 season.
Barcelona midfielder Xavi Hernandez said Atletico will "be a rival for the title until the end of the season."
"The game against Atletico is one of the most attractive matches in the league. They are playing like their coach wants, (and) Falcao can decide the match."
Falcao sat out Atletico's 3-0 win over Getafe in the Copa del Rey on Wednesday, but the Colombia striker is expected to be back for Sunday's match. Forward Adrian Lopez is a doubt after hurting his leg midweek.
Madrid is the clear favorite against Espanyol.
Espanyol is in the relegation zone with only one away win this season in seven games. It has lost its last three visits to Santiago Bernabeu Stadium by a combined score of 11-0.
Madrid could be without both of its first-choice strikers with Gonzalo Higuain still recovering from injury and Karim Benzema questionable after hurting his ankle in its 2-1 loss at Celta Vigo in the Copa on Wednesday.
This could open the door to youth player Alvaro Morata or see Cristiano Ronaldo spearing Madrid's attack.
Espanyol forward Sergio Garcia, back after a four-game ban for insulting the referee, said Celta's upset win would serve as an example to follow.
"Celta played well and was running hard all game long," Garcia said. "We have to take full advantage of the shots we get."
Saturday's top matchup is the Andalusian regional derby between Sevilla and visiting Malaga.
Sevilla striker Alvaro Negredo is in excellent form with 11 goals in all competitions this season and three in his last two games.
Sevilla thrashed Mallorca 5-0 in the Copa midweek, but it is in 11th place after only one win in its last seven league games.
Malaga is searching for its first victory in six away games to keep its hold on fourth place and Spain's last Champions League spot.
Several coaches are under pressure to get a much-needed win this weekend.
Joaquin Caparros' Mallorca was embarrassed by Sevilla in the Copa and hasn't won in 10 rounds in the league. Mallorca hosts the equally disappointing Athletic Bilbao on Saturday after the Basque side was eliminated from the Copa by third-division side Eibar.
Later Saturday, a Granada stuck in the relegation zone hosts a Real Sociedad side that hasn't lost in five games. Coach Juan Anquela is desperate for a victory to stop the calls for his firing at Los Carmenes Stadium.
Jose Oltra's Deportivo is in last place after four losses in a five-game winless streak. Deportivo hosts Valladolid on Monday.
Also on Monday, Celta looks to capitalize on its win over Madrid in the Copa as it hosts fifth-place Real Betis.
Elsewhere in round 16, Osasuna visits Getafe on Saturday, Real Zaragoza hosts Levante on Sunday after beating it in the Copa, while Rayo Vallecano is at Valencia.