Roger Federer was one win away from reclaiming the world No.1 ranking after he reached the semi-finals of the Stuttgart Open with a 6-4 6-4 win over Argentina’s Guido Pella.

Federer skipped the European claycourt season to concentrate on retaining his Wimbledon title next month and his plan appears to be working as the 36-year-old was in fine form on Friday.

The Swiss will also topple Rafael Nadal from the top spot if he reaches Sunday’s final.

Federer, who has won a record eight Wimbledon titles, was largely untroubled by Pella on Friday and lost just one point on serve en route to winning the opening set. He continued his momentum to clinch the victory in 65 minutes.

The 20-times grand slam winner will next face the winner of the match between Australian fourth-seed Nick Kyrgios and Spaniard Feliciano Lopez in the semi-finals.

Meanwhile, Canadian Milos Raonic battled to a 7-6 (7-2) 7-6 (7-1) victory against third seed Tomas Berdych, of Czech Republic, to set up a last four encounter against defending champion Lucas Pouille after the Frenchman ousted Denis Istomin 6-4 6-7 (7-5) 6-3.