Kei Nishikori is through to the third round of the BNP Paribas Open at Indian Wells courtesy of a hard-fought win over Ryan Harrison.

Nishikori looked to be in for a comfortable afternoon when he broke Harrison early on, but the Japanese struggled to hold his own serve in a frenetic opening few games in which he was broken three times.

However, Harrison struggled just as much on his own serve and Nishikori kept his cool to win the first set 6-4.

The US Open finalist then put his foot down at the beginning of the second and broke Harrison while starting to win on his own serve with regularity and comfort.

Harrison pushed for a breakthrough, but failed to find one and fell to a 6-4 6-4 defeat.