(CNN) — Missing Lionel Messi, La Liga champion Barcelona stumbled to a 1-0 defeat by Athletic Bilbao on Friday since the Spanish league season got underway in exciting fashion. Messi endured a calf injury throughout pre-season and with no Argentine, Barca looked fairly ordinary as replacement Aritz Aduriz’s stunning acrobatic volley in the game’s closing minutes sealed Bilbao’s shock win. “The contest has set us in our location,” Barca defender Gerard Pique told Bloomberg. “We were not us.” Last season, Barcelona coasted into the La Liga title, losing only three times and finished 11 points clear from second-place Atletico Madrid. Messi was the league’s leading scorer with 34 goals. But little went right for the Spanish winner on Friday. Barca striker Luis Suarez, who scored 33 goals last season, hit the post in the first half but soon afterwards limped off with the injury. “Tests completed on Saturday morning have confirmed that team participant Luis Su??rez has an injured right wing,” said Barca’s website on Saturday. “His comeback will soon dictate his return to action” READ: Real Madrid heads into the new year with more questions than answers READ: World’s finest soccer celebrities are playing too much Frenkie de Jong and Antoine Griezmann made their debuts for Barca, but it was the 38-year-old Aduriz who delivered the game’s magnificent finale. “Sometimes football can be so amazing,” Aduriz told reporters. “It’ll be impossible to not overlook this but everything has a start and an end. I’m incredibly thankful to have the ability to opt for this end.” Bilbao, who finished eighth last season, were well worth their win with striker Inaki Williams frequently troubling the Barca defense. READ: The isolation of the megabucks soccer star READ:’Adrian!” Liverpool’s goalkeeper is hailed by klopp Meanwhile, the Barca and Bayern Munich have reached agreement for the transfer of Philippe Coutinho into the Bundesliga team. The 27-year-old Brazil global will initially join on a season-long loan, together with Bayern with an option to make the deal permanent for the 27-year-old forward. “We’ve observed Coutinho for quite a while. The name doesn’t matter, only the caliber,” Bayern chief Karl-Heinz Rummenigge told the club’s website following the 2-2 draw with Hertha BSC in Friday’s Bundesliga opening match. “Obviously we have to finalise a few details, but we are thrilled to be bringing this player to Bayern,” additional Bayern sporting director Hasan Salihamidzic. Coutinho, who joined Barcelona for a reported $170 million in Liverpool in 2018, has fought to make an effect in Spain after filming in the English Premier League. He became the next most expensive player in history when he made the move to Barcelona.