Melbourne, Australia: Eighth-seeded Janko Tipsarevic retired from his fourth-round match at the Australian Open with an injured left foot while trailing Nicolas Almagro 6-2, 5-1 on Sunday.
The 10th-seeded Almagro advanced to a quarterfinal against fellow Spaniard David Ferrer, who beat Japan's Kei Nishikori in straight sets.
Tipsarevic said he injured the foot while changing directions during a rally late in the seventh game of the first set, and could barely walk on it afterward.
Fourth-seeded David Ferrer advanced to the Australian Open quarterfinals with a 6-2, 6-1, 6-4 win Sunday over an error-prone Kei Nishikori of Japan.
Ferrer will play the winner of the later Sunday match fellow Spaniard Nicholas Almagro and No. 8 Janko Tipsarevic of Serbia.
Nishikori made 65 unforced errors in the match, while Ferrer made just 24.
Ferrer is playing in his 41st consecutive Grand Slam tournament — he hasn't missed a major since competing in his first at the 2003 Australian Open.