Stuttgart - Roger Federer edged closer to displacing Rafael Nadal at the top of the world rankings as he dispatched Guido Pella 6-4, 6-4 at the Stuttgart Cup on Friday.
Top seed Federer needs to win on Saturday against Australian fourth seed Nick Kyrgios, who put out 2017 finalist Feliciano Lopez 6-4, 3-6, 6-3, if the Swiss is to return to the No 1 spot for the second time this season.
"I didn't think of number one during the match today, I was focused on the task at hand," said Federer.
"But when you play for number one (next match) I'm sure it will be in the back of my head."
The quarter-final victory in 55 minutes, which ended on a backhand, featured two breaks of serve for the Swiss, who executed well in his second match in three months after skipping the clay season and last playing in March.
"I was in good control throughout," added Federer.
"I served well and didn't give him too many chances to get into my service games.
"I thought I was able to stay aggressive, and cut down the length of the points, which I wanted to do."
Federer said that he was able to train briefly on the grass court of a friend in Switzerland but said that fitness work was the major part of his preparation after his absence from the clay court campaign.
"We used to have a shorter turnaround from clay to grass. Now we have many weeks to get ready (three weeks between the end of the French Open and start of Wimbledon).
"I was lucky to be able to get a few days on the grass before here, that was helpful."
Federer is aiming for a first title in Stuttgart after losing in the 2016 semis to Dominic Thiem and going out in an opening match a year ago to close friend Tommy Haas.
The 36-year-old won his 19th match from 21 played this season as his Wimbledon build-up continues on track.
At the All England club next month, the 20-time Grand Slam champion will be seeking a ninth title at the grass-court major.
Kyrgios turned in a much more relaxed performance against Spain's Lopez, admitting he even had fun on court.
"Today was fun, I played better than the first match," Kyrgios said. "It will be exciting to play Roger - for both of us."
At the bottom of the draw, Milos Raonic reached his second semi-final of the season to set up a clash with defending champion Lucas Pouille.
Raonic used his big-serving game to dominate a pair of tiebreakers in a 7-6 (7/2), 7-6 (7/1) defeat of Tomas Berdych.
"I got fortunate in the tiebreakers," the 27-year-old Canadian seventh seed said after reaching his first semi since Indian Wells last March.
The often-injured Raonic said that when he's healthy, he likes his game; he played just six matches from the end of Wimbledon last summer until the start of 2018.
"I can play well when my body allows. I wasn't ready for Australia (last January). But now that I'm back I'm playing well," said the player now coached by former great Goran Ivanisevic.
Raonic has beaten Pouille in both of their previous matches, both played in January, 2016, in Australia.
The French second seed overcame a nervous second-set to reach the semis 6-4, 6-7 (5/7), 6-3 victory over Uzbek Denis Istomin.
Results at the ATP Stuttgart Cup on Friday (x denotes seed):
Roger Federer (SUI x1) bt Guido Pella (ARG) 6-4, 6-4
Nick Kyrgios (AUS x4) bt Feliciano Lopez (ESP x8) 6-4, 3-6, 6-3
Milos Raonic (CAN x7) bt Tomas Berdych (CZE x3) 7-6 (7/2), 7-6 (7/1)
Lucas Pouille (FRA x2) bt Denis Istomin (UZB) 6-4, 6-7 (5/7), 6-3