Real Madrid have revealed that Gareth Bale only suffered a minor calf injury in the 2-2 draw with Villarreal.
Wales star Bale was forced off at half-time in the LaLiga encounter on Thursday.
Madrid had been leading 2-1 at the time, with Karim Benzema and Raphael Varane putting them ahead after Santi Cazorla's opener, but the former Arsenal man struck a late equaliser to deny the visitors all three points at Estadio de la Ceramica.
Bale underwent tests on Saturday and is set to miss Sunday's meeting with Real Sociedad.
A club statement said: "Following the tests carried out today on our player, Gareth Bale, by the Real Madrid medical department, he has been diagnosed with a grade 1 soleus muscle injury in his left leg. His recovery will continue to be assessed."
Real head coach Santiago Solari said during a news conference earlier in the day: "It looks to be something small. We hope he's back soon. There will be a test today and we'll have more information. He's someone very important for us."
Solari has backed Isco to replace Bale in the Madrid line-up, despite persistent question marks over his use of the Spain international this season.
"Isco has so much quality that he can play in any area of the pitch," he said. "Sometimes, you can be decisive with speed or with the final pass, with technical quality."
Solari also denied he is frustrated with full-back Marcelo, who has only managed 10 LaLiga appearances in 2018-19 due to fitness problems.
"He has had a very difficult first half of the season," he said of the Brazil international. "He's had several injuries and he's been recovering bit by bit. The trip to the Club World Cup, a small break... little by little, he's been picking up rhythm.
"He's an essential player for the team and for the club. It's key we don't injure ourselves. We have to take care of him.
"The most important thing now is to recover players and avoid them getting injured. Footballers are not machines"