A much-needed 2-1 win for Barcelona over Villarreal on Tuesday was marred by the sight of Lionel Messi receiving lengthy treatment and failing to emerge for the second half.
It was Messi's first start of the campaign having nursed his way back from a calf injury that restricted him to substitute appearances in Barca's first five La Liga games.
The Barca captain, who on Monday was crowned Fifa Men's Player of the Year, had to leave the field for treatment on the half-hour with the Spanish champions 2-0 up through Antoine Griezmann and Arthur goals.
Santi Cazorla pulled a goal back for the visitors on the stroke of half-time and Messi's involvement ended when he was replaced by Ousmane Dembele for the second half.
Ernesto Valverde said he took off Messi as a precautionary measure.
"He noticed a little bit of an issue with his adductor and we preferred for him not to stay on the pitch, but it was just a precaution," he said. "I don't think it's any more than just a niggle but we'll need to wait for tomorrow to confirm."
The victory takes Barcelona up to fourth with 10 points after six games, one point behind surprise leaders Granada, who shocked the Spanish champions 2-0 on Saturday, Athletic Bilbao, who visit Leganes on Wednesday, and Real Madrid ahead of their game at home to Osasuna the same night.
The win at Camp Nou brought some much-needed respite for Valverde and Barca, who had endured their worst start to a season in 25 years after collecting only seven points from their first five matches.
"We are playing well at home, but I think with the injury to Leo everyone was stopped in their tracks a little bit. I think we're very much on the right track at home, though."
Griezmann headed Barcelona in front after six minutes, darting in at the near post to meet a Messi corner.
Brazilian midfielder Arthur doubled the lead with a spectacular strike from distance as it appeared the Catalans would put their recent troubles away from home behind them, having lost to promoted Granada at the weekend.
It was the first time Messi, Griezmann and Luis Suarez had started a competitive game together for the club and the initial signs were promising.
However, Messi's injury resulted in a drop in tempo for the hosts allowing Villarreal to capitalise through Cazorla's long-range effort that left home keeper Marc-Andre ter Stegen red-faced as he misjudged the swerving shot.
Ter Stegen then made amends soon after as he turned away another Cazorla effort, before smartly rushing out of his goal to prevent Samuel Chukwueze from racing onto a through ball.
Barca's new starlet Ansu Fati was introduced for Suarez after 76 minutes, giving Barca a much-needed shot in the arm, firing narrowly wide before seeing strong claims for a penalty turned down in the closing stages as they saw out the win.
Barcelona visit Getafe in La Liga on Saturday before playing Inter Milan at home in the Champions League four days later.