Daniil Medvedev and Jannik Sinner have been replaced by Andy Murray and Jo-Wilfried Tsonga in the upcoming Rotterdam Open.
World number two Medvedev lost a thrilling five-set Australian Open final to Rafael Nadal on Sunday and does not feel ready to compete in the Netherlands.
The Russian explained his decision in a statement on Thursday, while Sinner has had to pull out due to COVID-19.
"Unfortunately I will not play in Rotterdam this year," Medvedev said.
"I just got back from Australia and am not ready to compete. Rotterdam is one of the favourite stops. I look forward to coming back in the future."
Roberto Bautista Agut and Borna Coric had already pulled out of the competition. Tournament director Richard Krajicek has confirmed that Murray and Tsonga, who won the event in 2009 and 2017 respectively, will now take part as wild cards.
Andrey Rublev is the reigning champion in Rotterdam after beating Marton Fucsovics in last year's final.