Nishikori survived a second set scare to defeat Almagro on Day 2 of the Australian Open.
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Nishikori survived an early scare against the Spaniard after going down a break of serve, however Nishikori won the next three games to hold Almagro at bay.
The Japanese up-and-comer went on to then save two break points before converting a his third set point win the first set.
A tight second set saw Almagro save three set points from Nishikori, before going down 7-1 to the fifth seed in a tiebreaker.
Nishikori made light work of Almagro in the third set, needing just 26 minutes to dispose to of the Spaniard.
Nishikori will now play the winner of Ivan Dodig and Joao Souza.