Stuttgart - Roger Federer shook off a stiff challenge from American teenager Taylor Fritz to reach the Mercedes Cup quarterfinals with a 6-4, 5-7, 6-4 on Thursday.
The match began the day but was halted by rain with the top-seeded Federer leading 4-3 with a break of serve. A return into the net by Fritz gave Federer the first set. Federer saved two set points before a forehand winner by Fritz and a forehand error by Federer gave the middle set to the 18-year-old American.
Federer struggled to hold serve early in the third but broke for 5-4 and clinched the match with a backhand winner.
Third-seeded Dominic Thiem edged Sam Groth 7-6 (3), 7-6 (2), and No. 4 Gilles Simon beat Jan-Lennard Struff 6-4, 4-6, 6-2.