BARCELONA, Spain (AP) -- The Champions League will offer either Barcelona or Atletico Madrid a spot in the semifinals and a boost in the racee to win the Spanish league.
Atletico leads Barcelona by one point in the Spanish league standings going into their fourth meeting of the season, with the three previous results all draws.
Atletico will be leaning on its stingy defense and striker Diego Costa in attack. But Barcelona forward Lionel Messi is scoring again as the team looks to reach the semifinals for a record seventh straight season.
Here are five things to know about Tuesday's game at the Camp Nou Stadium:
MESSI IN SYNC
Lionel Messi is scoring again, and that is rubbing off on Barcelona.
The Argentina forward has scored 17 goals in 12 games to take his season tally to 36 overall, and Messi is gaining steam at the perfect moment for a Barcelona team that had been unusually erratic at times this season.
"It is very important that the players remember what state we were in one week ago and how we are now," Martino said. "The biggest difference with Messi is related to us being at the end of the season."
IN COSTA'S IMAGE
Diego Costa's scoring spree continues as the Atletico striker netted his 33rd goal of the season in Saturday's 2-1 win at Athletic Bilbao, a performance coach Diego Simeone likened to the style of play of his star striker.
"Costa is as important to Atletico as Messi is to Barca," Simeone said. "Both are in great form right now, with Diego improving every day."
Costa left training at the Camp Nou on Monday early as he recovers from a leg muscle strain.
The Brazilian-born Spain striker has yet to find the back of the net against Barcelona this season but Atletico's chances of advancing will decrease significantly if he isn't 100 percent healthy for the game.
KOKE: XAVI'S SUCCESSOR
Barcelona and Atletico's matchup provides neutral fans with a masterful dose of the midfield maestros that have left Spain at the summit of world football, and will likely maintain it.
Xavi Hernandez has directed Barcelona and Spain's play for more than a decade, with the 34-year-old Barcelona midfielder winning nearly every trophy possible for club and country. Xavi has anointed Atletico counterpart Koke -- who assumes the same midfield duties for Atletico -- as the chosen one to lead the national team in the future.
"Koke is an extraordinary football player. He's got the talent, he's got the physical strength, he is the football player of the future," Xavi said. "He'll be the one pulling the strings for Spain's national team over the next 10 years."
Koke's emergence coincides with Atletico's improbable Spanish league run, with the 22-year-old Spain international nodding home the winner in Saturday's 2-1 victory at Athletic Bilbao that allowed Atletico to remain at the top of the table.
Atletico coach Diego Simeone called his team's 2-1 win at Athletic Bilbao one of the team's top performances of the season.
"I think we sent a clear message with our win in Bilbao," Atletico goalkeeper Thibaut Courtois said, with defender Diego Godin describing exactly how confident the players were.
"We've never felt inferior to anybody. If you look at this series, it's clear that Barcelona is the favorite but we know our strengths and with those we can do a lot of harm," Godin said. "We know what needs to be done to beat the top teams. If you look at Atletico over the past 2½ years, our style of play hasn't changed much, with our individual and collective effort being the keys."
Barcelona midfielder Andres Iniesta has put an uncharacteristically lukewarm start to the season well behind him.
The Spain playmaker has gotten stronger throughout the campaign, but has been particularly impressive lately.
"This is the best he's been all year," Barcelona defender Daniel Alves said. "Just when people think he's close to having peaked, he shows his ability again. I think he should have a Ballon d'Or in his trophy cabinet already. He's a player that has brought a lot to football."
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