Roger Federer is one match away from regaining the world number one ranking following his quarter-final victory over Guido Pella at the Mercedes Cup.
The Swiss beat world number 75 Pella 6-4 6-4 in 67 minutes in Stuttgart.
Federer dropped just 12 points on serve and saved both of the break points he faced against the Argentine to claim his 14th consecutive grass-court win.
He will face Nick Kyrgios in Saturday’s semi-finals, after the Australian beat Spain’s Feliciano Lopez 6-4 3-6 6-3.
Federer, a 20-time Grand Slam champion, needs to reach the final to replace Rafael Nadal at the top of the rankings.
Elsewhere, Australia’s Bernard Tomic reached his first ATP semi-final for two years with a win over Spain’s Fernando Verdasco at the Libema Open in s’Hertogenbosch.
Tomic beat the fourth seed 6-4 7-6 (7-3) to set up a meeting with either France’s Richard Gasquet or Greek Stefanos Tsitsipas.
In the men’s doubles, Britain’s Dom Inglot and Croatia’s Franko Skugor reached the final with a 6-4 6-7 (3-7) 10-6 win over Pole Lukasz Kubot and Brazil’s Marcelo Melo.