During the changeover following the fifth game of the second set in Sunday's Monte Carlo Masters final, Fabio Fognini had his already-taped ankle more heavily bound. He also had the trainer heavily wrap his right thigh. It looked as if he might not be able to finish the championship match against Dusan Lajovic, let alone win it.

Returning to the court, Fognini served his first ball. Lajovic engaged him in a long, spirited rally, testing Fognini's leg. The point ended when Fognini darted forward and heavily cut a backhand, sidespin drop shot -- his finesse so acute that even on television you could see him let his wrist go slack at precisely the right moment.

The ball floated across the net, kissed the clay, and curved on the bounce, out of court, just beyond the reach of a lunging Lajovic.

Fabulous Fabio's shot was remarkable and unpredictable, an apt symbol for the way the first of this year's Euroclay Masters events played out. Going in, the internet was aflame with anticipation of a final between the two top-ranked players in the world, Big Four icons Novak Djokovic and Rafael Nadal. Instead, the tournament produced a pair of first-time Masters finalists, including the lowest-ranked Masters finalist (No. 48 Lajovic) since 2001.

Fognini, the Italian touch artist seeded No. 13 (and winless on clay this year before the tournament), went on to win the title with a 6-3, 6-4 victory in the final. The effort capped a week of astonishing upsets and -- for the game's stars both young and old -- sobering realities.

.⁦⁦@fabiofogna⁩ joins the list of 1st-time #ATPMasters1000 champions (since 2017 Rome) with his title @RolexMCMasters. In the 17 previous Masters 1000 events the only player to win his 1st crown, ⁦@cilic_marin⁩ in 2016 ⁦@CincyTennis⁩. ⁦@TennisChannel⁩ pic.twitter.com/U8v9Qt5kjw — Greg Sharko (@SharkoTennis) April 21, 2019

Here are five things we learned during the course of a chilly, windy week in Monaco.

All bets are off for Roland Garros

Going back more than a decade, a member of the Big Four -- Djokovic, Nadal, Roger Federer or Andy Murray -- has won 33 of the 36 Masters 1000 titles on clay. Until Alexander Zverev won at Rome in 2017 (and Madrid in 2018), the lone "outsider" to take a clay Masters event was himself a Grand Slam champ, Stan Wawrinka (Monte Carlo in 2014).

Sure, the weather was lousy last week in Monte Carlo, but it has been challenging in many previous years as well. Yes, there were some truly improbable comebacks, but they were balanced nicely by tidy, artful beatdowns. And it's entirely possible that Nadal and Djokovic will round back into championship form before the French Open. It is, after all, a full month-plus distant.

But forget for a moment about those 30-something big dogs. The chief challengers of the ATP's graying poster boys were taught harsh lessons as well. Dominic Thiem, seeded No. 4 and considered the most likely successor to Nadal as a dominant clay-court expert, lost to Lajovic. No. 3 seed Zverev, a two-time Masters champ on clay, was knocked off by Fognini. That the winners of those two matches went on to contest the final tells us those upsets weren't flukes.

Monte Carlo hosted a comprehensive but not at all cockamamie breakdown of the ATP status quo. Maybe the old order can be restored in the coming weeks. Maybe not.

Rafael Nadal returned from injury at Monte Carlo, but his dominance on clay was tested in a thorough semifinal loss to eventual champ Fabio Fognini. Clive Brunskill/Getty Images

Rafael Nadal is on the brink

The No. 2-ranked player has never been easily discouraged. Nadal has fought back, on almost too many occasions to count, from injuries that sometimes approached career-threatening status. Over time, the stops and starts have taken their toll, eating away at the spirit as well as the game of the salty, leather-tough competitor.

Monte Carlo, where Nadal has won 11 titles and owned a 15-match winning streak entering this year's tournament, seemed like the ideal place for him to reassert his superiority on clay. It would also be the ideal place to wipe out the bitter aftertaste of that woeful loss to Djokovic at the Australian Open -- or the bitter, third-set tiebreaker loss against Nick Kyrgios in Acapulco. That was the last tournament Nadal played to completion before withdrawing from the tour for a month to rest his sore right knee.

Nadal, 32, seemed healed and ready to resume his place atop the clay game through three savagely efficient two-set wins in Monte Carlo. But Fognini, who has bamboozled Nadal on three previous occasions on clay, shut him down with comparable force in the semifinals.

"I probably played one of the worst matches on clay in 14 years," Nadal told reporters afterward. He went on to ruminate over the toll exacted by injuries that have prevented him from establishing continuity for about 18 months now. He said, "[It] is more difficult to hold sometimes the level every single day when you don't have confidence in tournaments in a row, or matches in a row."

Nadal has time to re-establish continuity over the coming weeks. But his status as the heavy favorite at the French Open is on hold.

Novak Djokovic isn't panicking. Yet.

Monte Carlo, where No. 1 seed and local resident Djokovic was a two-time winner, also seemed like an ideal place for Djokovic to hit the reset key. Unlike Nadal, Djokovic was not returning from injury. The 31-year-old Serbian star was merely returning from poor play that left the Australian Open champion a surprise loser relatively early at the two North American spring hard-court events.

Djokovic has won the past three Grand Slams, and he has an overwhelming lead in the ATP rankings (as of Monday, he has a 3,075-point lead over No. 2 Nadal). There's certainly no need for Djokovic to panic. But in many matches, including his three-set quarterfinal loss to Medvedev, his game lacked the lethal edge and aggression that carried him back to the top over the past nine months.

The most optimistic interpretation is that Djokovic is suffering from the "been there, done that" blues and needs the stimulation of a pending major to spark his best tennis.

Addressing reporters after his loss, Djokovic said of his recent passive streak: "I obviously still am lacking that determination to go for the shots maybe in some points. Just too many unforced errors. ... Maybe I'm lacking the consistency with the top results in the last couple of years in the best tournaments, but Grand Slams I have been playing my best, and that's what I intend to do."

The disruptors are writing the script

The players who upset the ATP applecart in Monte Carlo were not the usual suspects. Fognini will be 32 years old within a month. He's won a respectable eight titles but has been as mercurial and moody as he is gifted. If he experiences a late-career conversion to consistency, there's no end to the trouble he can cause his peers.

Lajovic, 28, had never won more than three matches at any given tournament, never mind an ATP title. His game has a DIY look, but it's more dangerous than it appears. And he's a scrapper.

Meanwhile, dangerous Jo-Wilfried Tsonga is on the mend, and Gael Monfils was playing torrid tennis until a strained Achilles forced him to withdraw at Indian Wells (Monfils is expected back for Estoril at the end of this month). Next Gen standouts Daniil Medvedev (who leads the tour with 21 wins in 2019 and knocked off Djokovic last week) and Borna Coric were solid in Monte Carlo, losing to Lajovic and Fognini, respectively.

Most important: Juan Martin del Potro, the disrupter-in-chief of the ATP Tour, is penciled in for Madrid early next month. And while it's ridiculous to cast No. 4 Roger Federer as a spoiler, he's coming off a two-year Euroclay hiatus and is also returning at Madrid. It appears he will have his hands full, but the Swiss icon might also end up driving the narrative.

Maybe next time for the Next Gen

The appealing fleet of rising 21-and-under players (and a few recent Next Gen graduates, including No. 8 seed Karen Khachanov) mainly took it on the chin in Monte Carlo. It was surprising to some, given how the youngsters had lit it up in the previous Masters event, last month's Miami Open.

Medvedev was the only powerful Next Gen force in the tournament. Khachanov, No. 6 seed Stefanos Tsitsipas, No. 15 Denis Shapovalov and wild card Felix Auger-Aliassime all fell by the wayside relatively early.

Tsitsipas made it as far as the round of 16, where he lost yet another tough three-setter to bitter rival Medvedev. The 23-year-old No. 10 seed from Russia -- a recent Next Gen graduate -- is now, at 4-0 in their series, officially in the head of Tsitsipas. Khachanov, a Masters champ himself (Paris in 2018), is a woeful 7-8 on the year.

It seems that no individual or cohort is immune to the volatility that is becoming the new ATP zeitgeist.