The return of Roger Federer to Euroclay and, ultimately, the 2019 French Open (he hasn't appeared at Roland Garros since 2015) has been the main storyline in the ATP this spring. But other factors have contributed to making these past few weeks perhaps the most exciting run-up to the French Open in years.

While Federer was searching for his clay game with notable success, Novak Djokovic and Rafael Nadal -- his two main rivals in the record book -- were playing hot potato with the label "favorite." They ended up splitting the two most prestigious Masters clay events, in Madrid (Djokovic) and Rome (Nadal). Fittingly, they finally met Sunday in the final of the Italian Open -- the last major match before the French Open.

But if you take the helicopter view, there's a lot more at stake for these three titans of the game than yet another Grand Slam title. Here's a look at what earning that title might mean for each man and how likely each of them is to succeed.

Novak Djokovic is on a Grand Slam roll. Clive Brunskill/Getty Images

ATP rank: No. 1

Record on clay 2018-19: 21-7

French Open career: 63-13

Best French Open result: Champion, 2016

What he has to gain: Djokovic has won the past three Grand Slams. Should he win the French Open, he will have completed a second "Djoker Slam," the term now used to describe the rare feat of the eponymous player holding all four Grand Slam titles at the same time.

The gold standard "Grand Slam" describes winning all four Grand Slam titles in the same calendar year -- something only the winner of the Australian Open in any given year can accomplish.

Djokovic is the Australian champion, so a Djoker Slam could evolve into a Grand Slam, leaving Djokovic just the third man in tennis history to record a Grand Slam.

What he has to lose: Djokovic has quietly crept close to Federer and Nadal in the Grand Slam singles title count. He now has 15, just two behind Nadal but still five short of Federer. Should Djokovic make the French final, he will be 32 years old. Federer, 37, has added only three major titles since he turned 32 (but has played in six finals). Djokovic can't waste any opportunity to win a major if he hopes to catch Federer.

Outlook: In January, ESPN analyst Brad Gilbert put the over-under on the number of majors Djokovic would win this year at three. The former coach of Andre Agassi and Andy Roddick backed Djokovic heavily through the spring, but after Nadal beat Djokovic in Rome, Gilbert said of their French Open chances, "They're 1A and 1B, with a razor-thin edge to Djokovic."

Djokovic and Nadal are in a similar situation. Both have absorbed some unexpected losses this year, leaving many wondering if they aren't more vulnerable than in the past. At other times, both have hit the familiar high notes.

When Djokovic won the Australian Open this year -- crushing Nadal in the most lopsided of the 13 Grand Slam matches they've played to completion -- he appeared poised to dominate. But things went a little sideways for him after that.

Djokovic struggled through the "Sunshine Double" portion of the early hard-court circuit, losing early at Indian Wells and Miami. He admitted that his training and focus were compromised by "way too many things off the court," which included his deep involvement in tumultuous ATP politics. Rising star Daniil Medvedev knocked Djokovic out of his first clay event, the Monte Carlo Masters.

Djokovic won Madrid in the nick of time, which will make it easier for him to digest his loss in Rome.

"We saw in Australia how slim the margins were," ESPN analyst Patrick McEnroe said. "Rafa was a little off, and all of a sudden Novak was a steamroller. Then in Rome, we saw how quickly things can change."

One worrisome stat for Djokovic, who often is described as the best serve returner in the game: He ranks 13th in winning return games among men who have played 10 or more matches on clay -- breaking 29.23 percent of the time -- with Nadal leading that pack at 42.5 percent.

Is Rafael Nadal all the way back from knee issues? Clive Brunskill/Getty Images

ATP rank: No. 2

Record on clay 2018-19: 40-4

French Open career: 86-2

Best French Open result: 11-time champion, including 2018

What he has to gain: Nadal could add to his already mind-blowing single Slam record by winning at Roland Garros for the 12th time. That also would draw him within two majors of Federer's record 20. Should Nadal surpass that record, the GOAT debate (in which Federer currently is the popular choice) changes, given that Nadal's head-to-head record against the Swiss icon already is a convincing 23-15. With a win in Paris, Nadal also would confirm that despite those recurring injuries, he can still reach his once-familiar heights.

What he has to lose: Never mind this era. It's unlikely anyone will ever usurp the throne of the "King of Clay." But losses to his main rivals would do more damage to Nadal's reputation than failure against, say, a rising young star such as Dominic Thiem.

A loss to Djokovic would provide the Serb star with a significant entry in his already positive series record (Djokovic leads 28-26) as well as a second French Open conquest. A loss to Federer at Roland Garros would be a startling first. Nadal is 5-0.

Outlook: Nadal has returned from a layoff of more than four months due to another bout of tendinitis in his right knee that sidelined him from September through December last year. When he returned at the Australian Open, he was rocked in a one-sided final by Djokovic.

Nadal attributed the painful loss to the compromised, compressed practice regimen forced by his knee problem. Those concerns were somewhat alleviated during the clay season. While he did not utterly dominate as in so many past years, the three losses he took were to quality players, including No. 4-ranked Thiem and fast-rising Greek star Stefanos Tsitsipas, ranked No. 6.

"The three guys who beat him were playing unbelievable," Gilbert said. "But best-of-five like in Paris is a different beast. It's much harder to sustain that brilliance, physically and mentally. That's the beauty of it."

At the Italian Open, Nadal handed Djokovic the first 6-0 set either man has recorded in their 54-match rivalry. Nadal had a chance to win that one swiftly, with Djokovic trailing 0-6, 3-3, 0-40, but Djokovic held serve and ultimately extended the match to three sets.

Yet there are real signs of vulnerability in the way Nadal failed to close out Djokovic in Rome in his familiar, merciless fashion -- despite the very slow start by Djokovic. Nadal has looked more nervous, made more unforced errors and dropped his groundstrokes short more often than in the past. Psychologically, this might be the most challenging French Open that Nadal has played in a long time.

"The one thing Rafa is missing because of those losses is the mystique he usually has at this time of year," McEnroe said. "But his style is still like nothing we've ever seen. That spin imparts with the forehand so ferociously and consistently for two to five hours. It's just an X-factor that's almost impossible to deal with."

Roger Federer hopes his return to clay will sharpen his game. Clive Brunskill/Getty Images

ATP rank: No. 3

Record on clay 2018-19: 4-1

French Open career: 65-16

Best French Open result: Champion, 2009

What he has to gain: A win would boost Federer's haul of major titles to 21. That ought to be enough to put the record out of reach for Nadal (17), who is 32 and frequently hobbled, as well as Djokovic (15). A victory in Paris also would give Federer a résumé-balancing second French Open title and add to his legacy, ranking as the most improbable of his many remarkable achievements.

What he has to lose: Federer going into Roland Garros personifies the expression, "He's playing with house money." Sure, a humiliating defeat dealt by a clay-court grinder on a cold, wet day would be a bummer for Federer and his fans. But Federer really is playing mostly for the fun of it.

Outlook: Federer has positioned his return to clay as a kind of busman's holiday, although he also has been thinking that playing on clay might leave him sharper for his priority -- the upcoming grass segment. He has been happy with his clay results, winning in successive tournaments against quality players after surviving match points (he defeated Gael Monfils in Madrid and Borna Coric in Rome).

Federer certainly got what he wanted out of his two clay events thus far: seasoning and a familiarity with the surface he hasn't officially played on since May 2016. So it's hardly surprising that although everyone has joined Federer in treating his return to clay as a lark, they're also keeping a close eye on his success and wondering where it might lead.

"Roger doesn't play the quintessential clay-court tennis, and I don't think he ever did," said Paul Annacone, who coached Federer from August 2010 through 2013. "Even when he was making those [five] Roland Garros finals. He's up on the baseline, he takes the ball early, he has variation in his attacks strategy, and he uses the drop shot."

It has been both delightful and edifying to watch Federer attack and play his brand of aggressive tennis.

"The way Federer is playing right now, nothing is beyond imagining," ESPN analyst Pam Shriver said. "He doesn't play a bad tournament anymore when he's healthy. Maybe sometimes he plays not so great, but his overall ability to play relaxed, smart, tactical tennis has made him a better player. If he's half a step slower, he's made up for it in his tactics."

Federer's clay game in Madrid was good enough to give Thiem, a master of clay, a great run for his money. But it's an inescapable fact that the French Open is like a towering mountain that poses an exhausting, extreme test for even the most accomplished climber. Federer has been to the summit only once because of Nadal's proficiency, and it was a decade ago.

"I don't think his chances to win are that realistic, but I believe he could make a good run," McEnroe said of Federer, whom he puts as a "fourth or fifth" favorite, behind Nadal, Djokovic, Thiem and Tsitsipas. "It's well within the realm of possibility that Roger will be a factor, but to expect him to go through two or three of those others at his age under the usual conditions in Paris is asking a lot."

About those usual conditions: Roland Garros is one place where conversations about the weather tend to be meaningful, not just idle chatter. Cold and wet days, which can be common during the French Open, create tough conditions more favorable to grinders than shot-makers. The best-of-five format also militates against creative players, as well as older and less fit or strong ones. To top it off, the French Open has refused to join its fellow majors in embracing a fifth-set tiebreaker.

Add it up. While we might see Federer produce some breathtaking tennis, the player most likely to emerge the winner is more likely Nadal -- or Djokovic.

As ESPN analyst and seven-time French Open champ Chris Evert said, "Roger is playing as good as I've ever seen him on clay, and Djokovic is right there with his game. I just think that over five sets on red clay, Nadal is going to be very hard to beat. For anyone."

In other words, it might be the same old story in Paris this year.