Novak Djokovic is one title - or five days - away from becoming the first tennis star to smash the $US100 million prize money barrier.
Djokovic's domination in 2016 has helped the Serb surge ahead of Roger Federer on the list of the sport's highest on-court earners and to within $US727,657 of the magical mark.
If he successfully defends his Rome crown this week to collect a fifth trophy in the Italian capital - and sixth title this season - the world No.1 will crack $100 million, a feat only Federer has come close to managing.
The Swiss superstar has earned $US97,958,429 in prize money during his 17-year, 17-slam career, compared to Djokovic's $US99,272,343.
If Djokovic is to achieve the financial milestone this week, the 28-year-old may have to topple his big-three rivals - Rafael Nadal, Federer and Andy Murray - in successive matches in the quarter-finals, semis and final to do so.
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After enjoying a first-round bye, the top seed opens his campaign against French qualifier Stephane Robert.
To beat Djokovic to the $US100 million mark, the second-ranked Federer, who has played just three matches since the Australian Open due to knee and back issues, would likely need to reign in Rome and reach the final - at least - at Roland Garros.
But even then, Djokovic would have to suffer an injury or early exits from both prestigious claycourt events.
Federer, though, remains the undoubted financial king of tennis as he closes in on becoming the sport's first-ever billion-dollar earner.
Backed by blue-chip sponsors including Nike, Rolex, Credit Suisse, Mercedes-Benz, Lindt and Moet & Chandon, Federer has been tennis's highest earner for nine years in a row, with Forbes estimating he raked in $US67 million in 2014-15.
On court, the prize money on offer these days to tennis's elite is mind-boggling.
Australia's first-ever world No.1 John Newcombe, a seven-times grand slam champion who topped the rankings in 1974, by comparison earned just $US1,062,408 ($A1.44 million) in prize money.
Pat Rafter, world No.1 for a week in 1999, made $US11,133,128 ($A15.12 million), in on-court earnings, while Lleyton Hewitt, who topped the rankings for a total of 80 weeks, amassed $US20,777,859 ($A28.22 million)
Three women - Serena and Venus Williams and Maria Sharapova - feature in the top-10 all-time prize money earners in tennis.
Serena comes in fourth overall with $US75,929,696 in on-court riches.
TENNIS'S BIGGEST PRIZE MONEY EARNERS
1. Novak Djokovic - $US99,272,343 ($A134.84 million)
2. Roger Federer - $US97,958,429 ($A133.05 million)
3. Rafael Nadal - $US78,007,139 ($A106.02 million)
4. Serena Williams - $US75,929,696 ($A103.20 million)
5. Andy Murray - $US44,339,508 ($A60.26 million)
6. Pete Sampras - $US43,280,489 ($A58.79 million)
7. Maria Sharapova - $US36,766,149 ($A49.94 million)
8. Venus Williams - $US32,798,0368 ($A445.47 million)
9. Andre Agassi - $US31,152,975 ($A42.31 million)
10. David Ferrer - $US28,839,132 ($A39.17 million)
