An MRI was scheduled for Thursday afternoon for the strain in his left hamstring, which he suffered in the final preseason game against the Denver Nuggets.
"He said it felt similar to the last one and we'll see how he is tomorrow, but that's a big blow for us because he's one of our leading scorers and rebounders, great player, and a lot of different ways we can use him," Kerr said. "So we're going to miss David but hopefully we're going to get him back 100 percent this time."
Draymond Green has started in Lee's power forward slot the past four games and had a career-high 24 points Wednesday night.
Lee scored six points in seven minutes in the first half and did not return.
Information from The Associated Press was used in this report.