It came as a surprise when Durant and the rest of the team arrived at the practice facility Friday that Westbrook, who had been seemingly indestructible, would be out.
In his fifth NBA season, Westbrook has never previously missed a game. He had the league's longest active streak of consecutive games played, with 394 straight regular-season games. He also has played in all 45 of Oklahoma City's playoff games, including last year's run to the NBA Finals.
"I think we all know Russell. He obviously wants to play. But at the end of the day, this was a medical decision," Presti said.
Backup Reggie Jackson figures to move into Westbrook's starting spot as the only other player with any significant time playing the point. Oklahoma City traded away former backup point guard Eric Maynor in February, getting only a trade exception and the rights to a Greek player with no NBA experience in return.
James Harden, who used to share some time at the point, is now on the opposite side as an All-Star for Houston.
Veteran Derek Fisher has previously played the point, but has been primarily used as a spot-up 3-point shooter in two stints with Oklahoma City.
Brooks wouldn't divulge his plans for how to replace Westbrook, but said Durant will have to take on even more playmaking duties.
"He's definitely going to have to be a guy that's going to have to handle the ball more. But he has actually for this past year has handled the ball more with that second unit," Brooks said. "He's always been somewhat of our point forward."
In general, the Thunder have avoided major injuries to their core players during their ascent into NBA title contenders. Durant has missed only five games over the past four seasons. His only time out of the lineup this season was the final game of the regular season, when he was healthy.
In total, the Thunder's starters missed only eight combined games all of this season. Westbrook, Durant and Serge Ibaka started every game of the 2011-12 season, and center Kendrick Perkins missed just one.
"Injuries are a part of sports and every team has to deal with them. Now, our team has to come together and make some adjustments," Presti said. "We've got a heck of a group of guys in our uniform, we've got a great coaching staff and it's going to take everybody in the building to pull together as we go forward, and our focus is on Game 3."
AP Sports Writers Kristie Rieken in Houston and Teresa M. Walker in Memphis, Tenn., contributed to this report.