Four-times Grand Slam champion Naomi Osaka and holder Barbora Krejcikova have pulled out of the Dubai Tennis Championships.
Osaka is still trying to find her feet on tour after returning to the circuit last month following a maternity break.
The Japanese player fell in the first round of the Australian Open and in Abu Dhabi, and lost to Karolina Pliskova in the Qatar Open quarter-finals on Thursday.
"I'm really sorry that I have to withdraw from the Dubai Tennis Championships this season," Osaka, whose last appearance in the event was five years ago, said in a statement on the tournament's website.
Former French Open champion Krejcikova, who won her maiden Dubai title last year after defeating world number one Iga Swiatek in straight sets, withdrew due to a back injury.
"This decision wasn't easy, especially given my fond memories and anticipation to compete again. However, my back injury requires further healing time. But I am committed to returning stronger next year," the Czech 28-year-old said.
Al Ain crushed 10-man Yokohama F Marinos 5-1 in the second leg of the Asian Champions League final on Saturday to register a 6-3 aggregate win and their first continental title in 21 years.
Fourteen-time French Open champion Rafa Nadal said there was still a chance this year's tournament in Paris may not be his last in comments ahead of his tough opener against fourth seed Alexander Zverev.
Outgoing Barcelona manager Xavi Hernandez said he was proud of his achievements with the club and was looking forward to being a fan again as he prepares to coach his final game against Sevilla.
World number one Novak Djokovic does not consider himself a favourite ahead of his title defence at the French Open, which begins with a first-round match against local hope Pierre-Hugues Herbert on Sunday.