The Croatian's place was taken by Thailand's Danai Udomchoke, who later lost to American Sam Querrey after receiving the late call-up to the first round.
Last week at the Devonshire Park, Ljubicic was forced out of his quarterfinal of the Eastbourne International against fourth-seeded Frenchman Fabrice Santoro after injuring his ankle in a heavy fall.
The 30-year-old has dropped to 30th in the world after being troubled by back and hamstring injuries last year.