Kei Nishikori and Juan Martin del Potro won in straight sets at the Swiss Indoors on Wednesday to stay on course for a quarterfinals meeting.
Third-seeded Nishikori of Japan eased past Paolo Lorenzi of Italy 7-6 (7-3) 6-2 in a second-round match.
Nishikori did not take any of his six break point chances in an error-strewn first set, and then upped his play in the second against the 38th-ranked Lorenzi.
Nishikori completed his second win of the week before Del Potro even stepped on court at Basel after winning the Stockholm title on Sunday.
Del Potro was playing his first match at the St. Jakobshalle arena since winning back-to-back finals against hometown favourite Roger Federer in 2012 and 2013.
The 42nd-ranked Argentine got a wildcard entry after long absences due to left wrist injuries, and beat 64th-ranked Robin Haase of the Netherlands 6-3 6-4 in the first round.
Del Potro next faces David Goffin, the fifth-seeded Belgian who lost the 2014 final to seven-time Basel champion Federer, who ended his season early.
Earlier, Richard Gasquet of France became the third seeded player to exit in the opening round. The seventh-seeded Gasquet, who won the Antwerp title on Sunday, retired when trailing 6-2 2-1 against Argentina's Guido Pella.
Eighth-seeded American Jack Sock, who lost the Stockholm final to Del Potro, made a winning start, 6-3 6-3 against Adrian Mannarino of France.
