(dpa) - Novak Djokovic knocked off Ernests Gulbis 6-3, 6-4 on Friday to produce his second win since May over his childhood tennis companion and reach the semi-finals of the Cincinnati Masters.
Djokovic, seeded third, stopped the teenager from Latvia in the French Open quarter-finals as the friends from the Niki Pilic academy in Munich several years ago begin playing each other at the top level.
Djokovic will face the winner from Rafael Nadal and Nicolas Lapentti. Nadal is moving closer to the number one ranking of Roger Federer after the Swiss lost in the third round to Ivo Karlovic.
The towering Croatian hit 24 aces in his quarter-final win over German Philipp Kohlschreiber 7-6 (8-6), 7-6 (7-3).
The 16th seed will take on Andy Murray, who reversed his form in dramatic fashion to reach a second straight Masters semi-final with a win over former champion Carlos Moya 2-6, 6-3, 6-1.
Second seed Nadal is poised to claim the top ranking held for four and a half years by Federer should he win the title on Sunday.
If he gets past his quarter-final, he can take over the top spot a week later as the Olympic event begins in Beijing.
Djokovic, a quarter-final loser to Murray a week ago in Toronto, lavished praise on fast-rising Gulbis.
"I've known him a long time, he's very talented and coming up - a rising star," said the 21-year-old Serb.
"He's a very powerful player.
"I knew I'd have to be consistent in order to win."
Djokovic needed a break per set to advance against the 19-year- old.
Murray looked like he would melt in the mid-30s Celsius heat on court in the torrid Midwest, before he rallied to prevent a disaster against Moya, Spain's former world number one and 2002 winner.
Murray squeezed through in just over 90 minutes. He saved a pair of break points in the third game of the second to avoid a second break which could have doomed his comeback chances.
Murray will compete in the fifth Masters semi of his career,having never gotten past that stage. "It was really tough at the start."
"I've never been to the final of a Masters but this looks like my best chance. I'm playing well enough and can hopefully come through."
The 31-year-old Moya was unable to get back into the game as Murray won six of seven games to level at a set apiece. The Scot ran away with the third to lift the comeback win.