British number one Kyle Edmund has pulled out of next month's tournaments in Marseille and Rotterdam.
The 24-year-old is still troubled by the knee injury that affected him at this month's Australian Open.
Edmund, who reached the semi-finals in Melbourne last year, was beaten in straight sets in the first round by Tomas Berdych last week.
He ended his 2018 season early after an MRI scan revealed a small amount of fluid behind his left knee in October.
Ranked 14th in the world at the start of the Australian Open, Edmund is poised to drop outside the world's top 25 when the latest list is published on Monday.
The injury setback follows a successful 2018, which included winning his first ATP title at the European Open in Antwerp in October.