Venus Williams has withdrawn from the Miami Masters with a back injury.
The 32-year-old was scheduled to face fellow American Sloane Stephens in the third round on Saturday before she was forced to pull out.
Stephens will now face defending champion Agnieszka Radwanska for a place in the quarter-finals.
Williams, who has won the tournament three times, had beaten Japanese veteran Kimiko Date-Krumm in three sets in the previous round.
