Christensen was forced off shortly after the hour mark at the Ramon Sanchez-Pizjuan and was visibly disappointed as he took his place on the bench. Gerard Martin came on as his replacement.
Barcelona have now confirmed that tests showed Christensen has suffered a muscle injury to the rectus femoris in his left quadriceps.
"Tests carried out have confirmed that first-team player Andreas Christensen has a muscle injury to the rectus femoris of his left quadriceps," the club said.
"He will be sidelined for the next few weeks, and his recovery will determine when he is available to return."
Hansi Flick had already indicated after the victory that Christensen would face a spell on the sidelines, although further tests were needed to establish the full extent of the problem.
The timing is particularly frustrating for Christensen, with the international break approaching. The injury means the Denmark international is expected to miss his country's upcoming UEFA Nations League fixtures.
Barcelona will now assess their defensive options ahead of the return to La Liga action. Gerard Martin stepped in against Sevilla, while Flick can also call on Eric Garcia and Jules Kounde depending on his defensive plans.
Barcelona's next league match is against Getafe at the Spotify Camp Nou on October 10, giving Christensen some time to begin his recovery before the fixture.
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