Top seed Milos Raonic booked his place in the San Jose 2013 semi-finals by beating Denis Istomin of Uzbekistan in straight sets 7-6 (0) 6-3.
Raonic, the two time champion here, will face American Sam Querrey for a place in the final.
Querrey advanced with a hard fought three sets win over Alejandro Falla of Colombia, eventually prevailing 6-3 4-6 7-5.
The American, who had a first round bye, was pushed to the limit by Lleyton Hewitt in round two, where the third set tiebreak had to decide about the semi-finalist.
Querrey leads the head to head against Raonic with 2-0, having defeated him both times in 2012. Their last encounter took place at the ATP Paris Masters, where the American emerged victorious with a 6-3 7-6 (1) win.