By Rory Carroll
INDIAN WELLS, Calif. (Reuters) - Canadian teenager Felix Auger-Aliassime won a battle of young guns by beating ninth seed Stefanos Tsitsipas 6-4 6-2 on Saturday to advance to the third round of the BNP Paribas (PA:BNPP) Open.
The 18-year-old, the youngest player in the world top 100, fired an unreturnable serve on match point to defeat the 20-year-old Greek -- the youngest player in the top 10.
While the outcome was an upset on paper, Auger-Aliassime held a 3-0 advantage over Tsitsipas when they met as juniors.
"I didn't know what to expect today because he's a completely different player (now)," said Auger-Aliassime.
"I believe in myself. I thought I had my chances. I served really well today, so that was obviously a big key."
Next up for last month's Rio Open finalist is either Japan's Yoshihito Nishioka or Spain's Roberto Bautista Agut, who play their second-round match later on Saturday.
American qualifier Marcos Giron battled back to down 23rd seed Alex de Minaur 1-6 6-4 6-2 for the biggest win of his career.
Playing in just his fourth ATP tournament, the Southern (NYSE:SO) Californian settled down after a shaky first set to dispatch the 20-year-old Australian.
Giron, 25, will be a heavy underdog when he faces Canadian 13 seed Milson Raonic, who pounded down 18 aces to send American Sam Querrey packing from Indian Wells for the second consecutive year with a 7-6(1) 6-4 victory.
France's Gael Monfils outlasted Argentina's Leonardo Mayer 6-4 3-6 6-3 under blue skies on the stadium court in Indian Wells.
With the win Monfils, who won last month's Rotterdam Open, improved his 2019 record to 13-3.
He will next face Spaniard Albert Ramos Vinolas, who upset 15th-seeded Italian Marco Cecchinato in their second-round meeting.