Sonego had only played one match against an opponent inside the Top 20 of the ATP Rankings (Isner, 2019 Miami) before taking the court against Khachanov. But the 23-year-old battled past the World No. 12 after one hour and 52 minutes.
The Italian qualifier, who defeated countryman Andreas Seppi in the first round, saved seven of eight break points en route to victory. Sonego owns an 8-6 tour-level record this season and reached his second ATP Tour quarter-final last week at the Grand Prix Hassan II in Marrakech (l. to Tsonga).
The 23-year-old will face Brit Cameron Norrie or Hungarian Marton Fucsovics in the third round. Earlier in the day, Norrie booked his spot in the second round with a 6-4, 6-3 victory against Frenchman Adrian Mannarino.
“We had a lot of long rallies. I think I was just able to defend a little bit better than him,” said Norrie. “When I found my first serve, I hit my spots well and had a high percentage winning on first points as opposed to him. I returned a lot better off the first serve against him.”
Gilles Simon twice recovered from a break down in the first set before claiming a 7-5, 6-1 win against #NextGenATP Australian Alexei Popyrin. The Frenchman will meet 13th seed Fabio Fognini in the third round.