Tsonga defeated Federer 7-5, 7-6 (3) in Toronto to take his second Masters 1000 title. It was Tsonga's first ATP Tour title win in 18 months. He also beat overall No. 1 Novak Djokovic, No. 9 Andy Murray, No. 8 Grigor Dimitrov and Federer, ranked No. 3, en route to the championship.
Suddenly, what appeared to be a two-man contest between Djokovic and Rafael Nadal has developed into a big question mark going into the U.S. Open. Anybody could win this thing.
Djokovic remains No. 1. Nadal is defending champion. Other than those two things, nothing is certain.
The next winner at Flushing Meadows could as easily be an up-and-comer such as Milos Raonic or Dimitrov, or it could be a late bloomer like Tsonga or Stan Wawrinka.
The uncertainty is exciting.
Unlike last year, when it was easy to bank on a floundering Federer or dominant Nadal, 2014 is a bit offbeat. Wawrinka struck the first errant chord with his win at the Australian Open. A perennial also-ran, Wawrinka worked his way into the top four.
Nadal's win at the French Open and Djokovic's victory at Wimbledon seemed to restore order. That was until Tsonga threw some extra funk in the mix. Then there's old-school Federer, offering a remix with his Edberg-esque serve-and-volley.
If Raonic continues dropping service bombs and Dimitrov keeps shedding his baby Fed, the U.S. Open could see another star born.
Meanwhile, Tsonga leads the field in the U.S. Open Series. His win in Toronto, Raonic's rise up the rankings and Dimitrov's increasing familiarity with later rounds have made the Big Four more mythical than ever.
The Big Four exists, of course. Djokovic, Nadal, Federer and Murray have won 36 of the last 38 Grand Slams.
However, make no mistake, the Big Four's grip on the ATP is slipping. The fourth player, Murray, will be ranked outside the top five. There are also questions about Nadal's U.S. Open readiness after he withdrew from the Rogers Cup and Cincinnati.
Going into the final, Federer held a 11-4 head-to-head edge over Tsonga. To win, Tsonga had to steady his nerves and play his game. He did.
The way in which Tsonga handled the pressure bodes well for his chances at Flushing Meadows. No matter how cruel the draw, it's unlikely he will have to go through four top-10 players in four days.
Djokovic will be playing in his first Slam since getting married. It's unclear if Nadal will even be playing in the U.S. Open.
The retooled Federer and reinvigorated Tsonga are among a fistful of possible winners. Right now, a number of players in the top 15 could snatch a chance and break up the stranglehold the Big Four have at the Slams.
Without a definitive favorite, the U.S. Open becomes even more intriguing, and the fans are the clear winners.