Williams has yet to complete a full practice with his new team. He strained his left calf the week before training camp opened and sat out several days, then injured his other calf midway through what was supposed to be his first full practice.
Coach Rick Carlisle said Sunday that Williams, who had an MRI on Saturday that confirmed the strain, will be kept out of contact drills for at least another week.
"He's doing better, but he will not play in the exhibition games," Carlisle said. "We'll see if we can get him ready for the opener. It's been a frustrating thing for him, but we're making progress. We'll get there. I just don't have a timetable."
Injuries were a factor in Williams' decline the past two seasons that led the Brooklyn Nets to give him a $27 million buyout to get out of the final two seasons of his maximum contract. Williams, 31, quickly signed with the Mavs after receiving the buyout, agreeing to a two-year, $11 million deal that has a player option for the second season, saying he hoped a fresh start could revive his career.
Williams, whose production dipped to 13.0 points and 6.6 assists per game last season, is one of three Dallas starters who has yet to play in the preseason.
Shooting guard Wesley Matthews (ruptured Achilles tendon) has been practicing full speed for the past week. Small forward Chandler Parsons (hybrid microfracture knee surgery) has yet to be cleared for any 5-on-5 work. Their statuses for the start of the regular season are also uncertain.