Toronto - Venus Williams was forced to draw on all of her vast experience before overcoming Czech youngster Katerina Siniakova to reach the last 16 of the WTA Toronto hardcourt tournament on Wednesday.
The 37-year-old American ninth seed, who began playing on the professional circuit before 21-year-old Siniakova was even born in 1996, eventually prevailed 7-5, 7-5 in 1 hour 39 minutes.
It was a satisfying win for Williams, who shrugged off the failure to convert a string of break points to raise her game when it mattered late in the second set.
Williams, who will be chasing her third US Open crown next month after reaching the Wimbledon and Australian Open finals this year, said she had remained calm against Siniakova even when errors prevented her from taking control.
At one stage Siniakova saved eight consecutive break points to ensure she always remained in touch. Williams eventually converted only four of 13 break points.
"She played so well, so competitive," Williams said afterwards. "I had a few errors but I think the key is to keep going for it and hopefully you'll get some in at some point.
"On those points she played some great tennis. And what can you do except go back and try again," Williams said of Siniakova's multiple break-point saves.
Williams will now face Elina Svitolina in the next round.
Wimbledon champion Garbine Muguruza advanced with a 7-5, 6-2 win over Belgium's Kirsten Flipkens.
Top seed Karolna Pliskova of the Czech Republic meanwhile eased past Russia's Anastasia Pavlyuchenkova 6-3, 6-3.
It was Pliskova's first match since she was installed as the current world number one and she confessed she had been nervous beforehand.
"I had a little bit of nerves before the match, but during the match I felt much better, especially at the end," Pliskova said.
"I played doubles yesterday so the nerves went out a little bit yesterday, and I felt good today. I'm definitely happy that I'm through to the next round."
Two seeded Russian players were among those to make an early exit.
Svetlana Kuznetsova, seeded eight, was the highest-profile casualty, tumbling out to Catherine Bellis of the United States 6-4, 7-5.
Elena Vesnina, the 16th seed, was sent packing by Australia's Ashleigh Barty.
Barty, a 21-year-old Queenslander who has also played professional Twenty20 cricket, won a gripping three-setter 6-3, 5-7, 6-4.
But there was better news for the Russian contingent as Ekaterina Makarova saved two match points and recovered from a set down to end seventh seed Johanna Konta's challenge.
Konta, playing her first match since losing in the Wimbledon semi-finals last month, was beaten 5-7, 7-6(7/4), 6-3.
Other seeds to fall by the wayside on Wednesday included Latvia's Anastasija Sevastova and Dominika Cibulkova of Slovakia.
Fifteenth seed Sevastova crashed 6-3, 6-4 to Japan's Naomi Osaka while Lucie Safarova accounted for 11th seed Cibulkova 6-2, 6-4.
Results on Wednesday in the WTA hardcourt tournament in Toronto (x-denotes seeded player):
Angelique Kerber (GER x3) bt Donna Vekic (CRO) 6-4, 7-6 (7/5)
Karolna Plskov (CZE x1) bt Anastasia Pavlyuchenkova (RUS) 6-3, 6-3
Naomi Osaka (JPN) bt Anastasija Sevastova (LAT x15) 6-3, 6-4
Agnieszka Radwanska (POL x10) bt Timea Babos (HUN) 6-0, 6-1
Sloane Stephens (USA) bt Petra Kvitova (CZE x14) 7-6 (7/4), 3-6, 6-2
Lucie Safarova (CZE) bt Dominika Cibulkova (SVK x11) 6-2, 6-4
Ekaterina Makarova (RUS) bt Johanna Konta (GBR x7) 5-7, 7-6 (7/4), 6-3
Venus Williams (USA x9) bt Katerina Siniakova (CZE) 7-5, 7-5
Ashleigh Barty (AUS) bt Elena Vesnina (RUS x16) 6-3, 5-7, 6-4
Garbie Muguruza (ESP x4) bt Kirsten Flipkens (BEL) 7-5, 6-2
Catherine Bellis (USA) bt Svetlana Kuznetsova (RUS x8) 6-4, 7-5
Caroline Garcia (FRA) bt Varvara Lepchenko (USA) 6-1, 6-4
Simona Halep (ROM x2) bt Magdalena Rybarikova (SVK) 6-3, 6-4