Ibaka had a magnetic resonance imaging (MRI) scan on his left calf on Friday and is "expected to miss the remainder of the 2014 postseason," the Thunder said in a statement.
The 24-year-old suffered the injury during the third quarter of Thursday's 104-98 series-clinching win over the Los Angeles Clippers.
"We are obviously disappointed for Serge, as he is a tremendous competitor, and we know how badly he wants to be on the court with his teammates," said Thunder General Manager Sam Presti.
Ibaka, who is known for his shot-blocking skills, has been averaging 12.2 points, 7.3 rebounds and 2.23 blocks per game during the playoffs.
He led the National Basketball Association in total blocks during the regular season for a fourth consecutive year after recording 219 blocked shots.
"At this point it is important that our team directs its concentration and energy towards preparation and execution for our upcoming series," said Presti.
"As with all teams, our group has confronted different challenges. It is our collective experience that we will call on to ensure that we play to our capabilities."
The second-seeded Thunder, beaten in five games by the Miami Heat in the 2012 NBA Finals, will take on the top-seeded Spurs in the best-of-seven Western Conference finals, starting on Monday in San Antonio.
- Sports & Recreation
- Los Angeles Clippers
- magnetic resonance imaging