After Saturday's morning shootaround, Mavs coach Rick Carlisle said West is dealing with a stomach illness and was vomiting Friday night after the team arrived at its hotel.
Losing West would serve as a major blow to Dallas, particularly on the defensive end.
West, the starting shooting guard, would have first crack covering explosive Thunder point guard Russell Westbrook, and also would see significant time defending the league's leading Sixth Man of the Year candidate, James Harden.
"We've got a Plan B," Carlisle said. "I'm not going to get into the details of it. We'll see where he's at game time. Other than that, we're ready to go."