PARIS -- Three startlingly young and talented tennis players -- Borna Coric (18 years old), Thanasi Kokkinakis (19) and Nick Kyrgios (20) -- have hurtled across the ATP World Tour sky for the past year, like a fizzing, fiery comet.
They are the next generation, as acknowledged by everyone from Roger Federer to Rafael Nadal. But in some ways, their success has obscured the steep trajectory of 22-year-old Nebraskan Jack Sock, who is still only the age of a typical college senior.
Playing the relatively new role of venerable veteran Saturday, Sock schooled one of those youngsters, Coric, by the sobering score of 6-2, 6-1, 6-4.
"It was a good day for me, for sure," Sock said later.
Because Coric played so far behind the baseline, Sock explained, he was able to maneuver him around the court and dictate points.
Coric, who has been compared to the young Novak Djokovic by Djokovic himself, was trying to become the youngest man to reach the fourth round of a major since Marat Safin here in 1998. But it is Sock who finds himself the youngest male in the men's round of 16 -- his first in a Grand Slam singles event -- and the last American man left in the draw.
Sock is also the youngest American into the Roland Garros round of 16 since Pete Sampras, who was 21 years, 9 months old when he did it in 1993.
And now, Sock will get the ultimate test Monday: Nadal, the King of Clay, almost certainly on Court Philippe Chatrier, where he has won nine French Open titles.
Sock's might be the feel-good story of the season, for Sock has overcome a ton of adversity -- that, in a weirdly fortuitous way, has worked in his favor -- in a short period of time.
• Following pelvic surgery in December, Sock missed the first two months of the season. In Kansas City, he used those nine weeks to get into the best shape of his life with a ruthless trainer who has worked with NFL players.
• In January, his older brother, Eric, lay in a hospital bed with a combination of pneumonia and Lemierre's syndrome, a severe throat infection that left him unable to breathe on his own for more than a week.
• After a harrowing three-week stay, Eric was released and, in a sense, so, too, was Sock.
In his first match back, at Indian Wells in mid-March, there were tears in Sock's eyes when he defeated Yen-Hsun Lu in straight sets.
"It's just a good reminder out there that obviously this is my career and my living and everything," Sock said in his postmatch news conference, "but it kind of puts in a different perspective and you're playing for more. When you're out there and get frustrated missing a ball or whatever it is, you kind of think what he's been through, almost not making it to a kind of miraculous recovery."
There is no one swinging freer at Roland Garros than Sock. He's got one of the fastest forehands in the game, in terms of speed and the ball's revolutions per minute, the result of an uber-extreme western grip.
After beating Coric, Sock was asked what he was most curious about regarding his match with Nadal.
"I'm kind of excited to see the forehand-to-forehand battle," Sock said. "Obviously we are both going to be trying to do similar things. It will be pretty interesting to see the different game plans going on. Obviously we are both looking to hit forehands. For me, the ad side of the court and him the deuce side of the court obviously and try to find the other's backhand and maneuver the ball around. I think it will be kind of a chess match and who can find the forehand first and kind of open up the court."
At the very least, Sock -- who loves clay more than any other surface and reached the third round here a year ago -- will see his ATP World Tour ranking rise to a career-high No. 31 or 32 after the French Open.
Even with his unprecedented success, there is more sorrow for Sock.
His grandfather is suffering from Alzheimer's and is under 24-hour care. Before the tournament, Sock tweeted: "You'll be with me on the court in Paris grandpa. Stay strong in your battle with Alzheimer's. I love you."
He's been playing with this message written on his shoes: #4Ugpa
Sock called his grandfather after his first-round victory, but his grandfather couldn't answer when his grandmother held the phone to his ear.
"He's got tubes in his throat," Sock said. "He's lost a bunch of weight and not looking great. But it's part of life. I hope he lasts just as long as he can, and then hopefully after this tournament I can get back and hopefully go see him."