MADRID (AP) -- Atletico Madrid's impressive Spanish league campaign finally gets the ultimate test as it comes up against co-leader Barcelona, which has Lionel Messi back from injury.
Messi marked his return from a two-month layoff with a pair of goals in Barcelona's 4-0 Copa del Rey victory over Getafe on Wednesday. Atletico, meanwhile, drew 1-1 at Valencia in the midweek domestic cup competition that has been a distraction with Saturday's league clash looming.
Barcelona and Atletico both have 49 points from 18 games, while Real Madrid is third with 44 points.
Here are five things to know about the Spanish league this weekend:
Atletico would show once and for all that it's a legitimate title contender if it emerges from Saturday's match at the Vicente Calderon Stadium alone in first, a spot the team has not occupied at this point of the season since it last won the championship in 1996.
"Winning on Saturday will be insignificant if we don't meet our objectives over the season," Atletico midfielder Koke said. "We've got the entire second half of the season to go even though we all realize that up until now this is the most important game of the season."
Atletico defender Juanfran Torres is available after having a booking revoked, avoiding a ban.
Atletico will have to prepare for Messi, who seems to be back to his normal self after a torn left hamstring, scoring one of his goals from a typical run through the opponent's defense.
"What I wanted was to get back on the field and to play. I was very motivated to return," Messi said. "It was hard keeping my spirits up over these months but determination was always there."
Neymar was absent because of a stomach bug but the Brazil striker should return against Atletico. Goalkeeper Victor Valdes could also be back.
"The team showed how good it was and that nobody is untouchable," Messi said. "This is a squad that responds to its demands."
Both Atletico and Barcelona owe their league runs in part to Argentine coaching.
Barcelona coach Gerardo Martino replaced Tito Vilanova for this season, while Atletico counterpart Diego Simeone has nurtured his team since taking charge in December 2011.
Martino lauded Simeone's work, which has included Europa League and Copa del Rey triumphs. Atletico is not only a Spanish league contender but a Champions League favorite after a near unbeaten group stage.
"What Diego Simeone has done at Atletico Madrid is incredible," Martino said. "The squad has grown stronger since his arrival, it's not the same one that (Simeone) took on when he got there."
With all the attention on Atletico-Barcelona this weekend, Real Madrid is hopeful of making up ground.
Madrid, which is at Espanyol on Sunday, is unbeaten in 13 games ahead of Thursday's Copa del Rey match against Osasuna with its last loss coming against Barcelona in October.
"We're hopeful that this game will allow us to recover some points on the leader, but if we win on Sunday it won't be because Barcelona or Atletico didn't win," coach Carlo Ancelotti said.
Ancelotti said Madrid has no plans to tap the January transfer window to bolster its team, which has a healthy Gareth Bale and Cristiano Ronaldo available.
Angel di Maria is available after Madrid opened and closed a disciplinary case against the talented Argentina forward over an awkward on-field gesture.
Di Maria quickly grabbed his crotch as he came off for Gareth Bale in last weekend's league victory over Celta Vigo, which led to accusations that he had directed a rude gesture toward Madrid's fans or Ancelotti.
Di Maria had the support of Ancelotti over the incident, which the player said was blown out of proportion.
"It was just a natural gesture that any man would make when he's running. It wasn't directed at the fans or the coach like is being said," Di Maria said in a video posted on Madrid's website. "The truth is that if I have upset people I'm sorry, but it's just as I have explained."
Madrid closed the case on Thursday.
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