Tim Duncan scored 27 points as San Antonio took advantage of Ibaka's absence to dominate, beating the Oklahoma City 122-105 night in the opener of the Western Conference finals.
Tony Parker did not appear limited by a hamstring injury, scoring 14 points and having 12 assists in 36 minutes.
The Thunder got their usual offensive outputs from All-Stars Kevin Durant and Russell Westbrook, who scored 28 and 25 points respectively.
But Oklahoma City's remaining starters, Nick Collison, Thabo Sefolosha and Kendrick Perkins, combined to score five points with 13 rebounds and one assist.
But it was defensively were the Thunder struggled without Ibaka, who will miss the remainder of the postseason after injuring his calf muscle in Oklahoma City's series clincher against the Los Angeles Clippers.
Spurs' improving accuracy
The Spurs shot 58 percent from the field, which was the highest shooting percentage allowed by the Thunder in the postseason since relocating from Seattle.
Parker, who picked up a mild hamstring strain in San Antonio's series clincher against Portland, drove the paint and dished to Duncan early before looking for his own shot midway through the quarter.
Parker scored all but two of his points in the first half as the Spurs beat the Thunder for the first time this season.
Even though San Antonio improved to 7-1 at home in the playoffs, winning their past five games by an average of 20.6 points, this victory was particularly hard fought.