Daniil Medvedev was sent crashing out of the ATP/WTA Indian Wells Masters in a stunning defeat to Gael Monfils on Monday that ended the Russian's three-week reign as world number one.
On a day of upsets in the California desert, Medvedev was the highest profile casualty to be sent packing, outfoxed 4-6, 6-3, 6-1 by veteran Frenchman Monfils.
Brooksby, ranked 43rd in the world, advanced to the last 16 with a 1-6, 6-3, 6-2 win.
Earlier, the 35-year-old Monfils scored his first victory over a world number one since 2009 with a superb display to dispose of US Open champion Medvedev.
The defeat means Novak Djokovic will on Monday return to the top of the world rankings, three weeks after Medvedev became number one.
Monfils sealed victory in 2hr 6min after converting his sixth match point.
"I'm in my zone and I'm a tough opponent for anyone," Monfils said. "It's been a long time since I've beaten a world number one, so I'm pretty happy."
But after Monfils took the second set -- clinching with a cheeky underarm serve -- Medvedev's composure evaporated in the decider.
The Russian earned a code violation for smashing his racket in frustration after being broken in the first game, and Monfils raced through the gears to seal a deserved victory.
Medvedev said he would aim to reclaim his number one ranking at the Miami Open next week.
"Now I know I'm going to lose it (the ranking), so I have Miami to try to get it back," Medvedev said.
"Usually feeling a little bit better in Miami in terms of tennis, so we'll try to play good there.
- Nadal marches on -
"When I play my best tennis, my good tennis, it's really tough to beat me. But that's the toughest part of tennis is to reproduce it time after time."
Monfils, the 26th seed, will face talented young Spaniard Carlos Alcaraz in the fourth round.
Alcaraz, seeded 19, advanced to the last 16 with a confident 6-2, 6-0 demolition of compatriot Roberto Bautista Agut, the 15th seed.
As Medvedev was left reflecting on his early exit, Rafael Nadal's unbeaten start to 2022 continued with a straight-sets defeat of Britain's Dan Evans.
The 21-time Grand Slam champion recorded his 17th straight victory of the year with a 7-5, 6-3 defeat of the 27th seed.
"Today was a step forward," Spain's Nadal said. "There is no other chance but play very well the next day if I want to keep going. If not, I'm going to go home."
Nadal will play Reilly Opelka in the last 16 after the American 17th seed downed Canada's Denis Shapovalov, seeded 13, 6-7 (4/7), 6-4, 6-4.
- Azarenka tears -
In the women's singles, Veronika Kudermetova advanced to the last 16 after her Czech opponent Marie Bouzkova retired in the second set at 6-4, 0-2.
Greece's Maria Sakkari, looking to build on a breakout 2021 which included two Grand Slam semi-finals appearances, overwhelmed another Czech, Petra Kvitova, in straight sets.
Sakkari booked her place in the fourth round with a 6-3, 6-0 win over the two-time Wimbledon champion.
After the tearful exit of four-time Grand Slam champion Naomi Osaka on Saturday, there was another emotional flashpoint as Victoria Azarenka succumbed to Kazakh 17th seed Elena Rybakina 6-3, 6-4.
Rybakina's victory was overshadowed by a bizarre incident which came while Azarenka prepared to serve while trailing 6-3, 2-2.
Play was held up for several minutes as the 32-year-old two-time Australian Open champion dissolved into floods of tears, waving away intervention from the chair umpire saying "I'm sorry, I'm really sorry."
Rybakina described the incident as a "very strange situation".
"I just hope everything is good with Vika because I don't know what happened," she said. "Hope everything is okay."