Lionel Messi, who made his first start for Barcelona in the 2019-20 season after returning from a calf injury, was replaced after half-time as the forward suffered a thigh problem.
Messi made his 400th La Liga start for the Spanish champions but things once again went awry for him.
However, Barca beat Villarreal 2-1.
Here's more on the same.
Messi replaced by Dembele as Barca win 2-1
Messi made an assist for Antoine Griezmann with a floating corner in the sixth minute.
Seven minutes later, Arthur made it 2-0 after collecting the ball from 30 yards out.
Messi took treatment on the sideline after suffering the injury before carrying on until half-time.
Just at the stroke of half-time, Santi Cazorla pulled one back.
Messi was replaced by Ousmane Dembele after half-time.
Ernesto Valverde provides update on Messi
"When something happens to Messi, everyone stops, not only on the field, but in the stands as well," Ernesto Valverde said. "As a precaution we have decided not to risk it. In theory, it is nothing more but we will see tomorrow how it is."
Messi wins best men's player of the year award
Meanwhile, Messi won FIFA's Men's Player of the Year award on Monday.
Messi bagged the award for the sixth time in his career after being voted the best in 2009, 2010, 2011, 2012 and 2015.
The Argentine superstar made 58 appearances for club and country in the 2018-19 campaign.
Messi edged out Cristiano Ronaldo and Virgil van Dijk for the prestigious award.
Barca cannot afford to lose Messi
Barca cannot afford to lose Messi for the upcoming matches.
They have collected 10 points from six games so far.
Barca have struggled with Messi being unavailable and one will hope that the injury isn't as serious.
This could increase the pressure on Valverde.
Meanwhile, Griezmann expects Barca to improve.
"We are still far from our best but with matches everything will improve."
Granada go atop of La Liga, Real Betis beat Levante
Elsewhere, newly promoted outfit Granada are in top of La Liga table with 11 points from six games. They managed a draw against Real Valladolid. Meanwhile, Real Betis overcame Levante 3-1.