Top-seeded Serb Ana Ivanovic withdrew from the Qatar Open on Thursday after injuring her left ankle beating Olga Govortsova of Belarus the previous day.
The $2.5 million (1.28 million pound) tournament then lost second seed Svetlana Kuznetsova of Russia, who was beaten 6-3, 7-6 by Austrian left-hander Sybille Bammer.
Ivanovic, runner-up to Maria Sharapova at last month's Australian Open, slipped on the baseline when leading Govortsova 6-3, 5-1 and struggled to finish her second-round match on Wednesday.
"It's still pretty painful and hard for me to step on. I'm very disappointed the way I had to end this tournament," Ivanovic told reporters.
"I was icing my foot all night. I had to wake up every hour so I didn't get much sleep but hopefully the team around me can help me to recover as fast as I can."
Ivanovic said she had not suffered a major tear.
"It's a strain, an overstretch of the ligaments," she said. "There's not any major tear, which is definitely good, but there are a few micro-tears there.
"I still get a lot of pain and have to keep icing my foot and keep it compressed and elevated to try to keep the inflammation down."
Ivanovic hopes to compete at the Dubai Tennis Championships next week where, because of a first-round bye, she would not have to play until Wednesday.
Kuznetsova had struggled to overcome windy conditions on Wednesday, and the weather again proved to be as much of a challenge as her opponent.
Bammer put Kuznetsova under pressure from the start, breaking in the opening game, and went on to take the set.
Kuznetsova then served for the second set at 5-4, and after holding four set points surrendered the match on Bammer's fourth match point when she netted a backhand.
In the windy conditions, play was interrupted three times during the final point by paper blowing across the court.
"I started to play better in the end, but in these conditions it was pretty impossible to play a normal game," Kuznetsova said. "Playing bad I still had chances, so this is disappointing."
The Russian considered that play should not have taken place in such conditions.
"I think so, yes," she said. "It was a few times in my head, 'Will they cancel this because this is a disaster'. I couldn't play the ball and it was embarrassing to stay there, but I was still fighting to try and get this match somehow."
