MADRID (AFP) - Kei Nishikori ensured he will become the first ever Japanese player to make the top 10 of the ATP rankings with a 6-4, 6-4 win over Spain's Feliciano Lopez to make the Madrid Masters semi-finals on Friday.

Currently ranked 12th in the world, Nishikori will move into the top 10 when the latest rankings are released on Monday thanks to 13-match winning streak.

The 24-year-old reached the semi-finals of the Miami Masters in March before having to withdraw due to a groin problem and won his first ever tournament on clay on his return from injury at the Barcelona Open two weeks ago.

"It was a big goal for me to get to the top 10, but it is only one week for now so I have to keep playing better tennis to stay in the top 10," he said.

"My goal is not just to be there for one week so hopefully I can keep that ranking for a while." Nishikori was bothered by a back injury throughout the second set against Lopez.

However, he is hopeful of being fit to face David Ferrer in the last four on Saturday.

"It should be ok. I don't know for sure, I only have half a day to recover so it's going to be hard but hopefully I will be ok."