Will Serena's US Open controversy, Federer's woes carry over to 2019 tennis season?

The US Open final between Serena Williams and Naomi Osaka might have a lasting impact beyond the drama that ensued down the stretch. Cynthia Lum/Icon Sportswire

Surprises happen. In tennis, they happen a lot. This year, it all started in a big way when Caroline Wozniacki -- long known as the "best WTA player not to have won a major" -- ran the table to capture the Australian Open. The important thing about surprises, though, is their lasting impact, whether it's a popular one or not. With that in mind, let's look at some of the major surprises of 2018 and see how they might resonate in the year to come.

1. The US Open women's final

Naomi Osaka's title in New York was not an earth-shattering surprise for knowledgeable tennis fans, but the way the final played out was utterly unexpected. Serena Williams' meltdown was as uncharacteristic as it was surprising. Sure, she spent most of the year trying to find her game following maternity leave, but her 2018 results suggest Williams will never dominate the way she once did.

Williams lost two major finals in 2018 and, among other setbacks, suffered the worst loss of her career, a 6-1, 6-0 drubbing to Johanna Konta at the Silicon Valley Classic. Williams is 37 years old, and competition on the WTA Tour is more intense and cold-blooded than ever. Her peers respect her more and fear her less than ever before. Williams might bag that elusive record-tying 24th Grand Slam singles title, but it's hard to see her towering over the field.

2. The reinvention of the Davis Cup

This was a stunning coup for reformers and a bitter blow to those who loved the competition. The ITF didn't just streamline the Davis Cup; it destroyed the event. The new entity (starting in 2019) will be a single-site, single-week event designed to lure the top players back into the Davis Cup fold. The ITF also was enchanted by the potential revenue the new event might generate. In many ways, it's a roll of the dice.

The change will free up as many as three weeks on the ATP calendar for many members of the 18 teams that qualify for the new event. But the reception to the reform among impact players has been lukewarm. If the top names choose to sit out the event and the tournament fails to generate fan interest and media hype, the Davis Cup will be dead. Perhaps not in 2019, but soon.

3. Journeyman John Millman's upset of Roger Federer

This came on a swelteringly hot night at the US Open. It was a stunning men's Grand Slam result rivaled only by Novak Djokovic's loss at the French Open to No. 72 Marco Cecchinato a couple of months earlier. But Djokovic was still in the throes of a long and painful slump, while Federer seemed to be firing on all cylinders as he entered the fourth-round match.

Federer, who turned 37 just weeks earlier, blamed the US Open loss on the stifling, brutally humid conditions. ("It was just one of those nights where I guess I felt I couldn't get air. It's one of the first times it's happened to me," he said.) Whatever the reason for Federer's shockingly flat performance, it was yet another sign that age is catching up with the all-time men's Grand Slam singles leader. Come January, he'll enter the Australian Open as defending champion. Watch closely.

4. Wimbledon finally adopts a fifth-set tiebreaker

This decision followed three overtime matches at the All England Club (two of them semifinals) that wrought havoc with the scheduling and fitness of the competitors. The tipping point was Kevin Anderson's 26-24-in-the-fifth semifinal win over John Isner. A tiebreaker will be used to end fifth sets that reach 12-all starting in 2019.

We can expect more risk-taking and exciting shot-making in fifth sets at Wimbledon in the future, with fewer matches going into overtime. Until now, players tended to dial back risk once the fifth set commenced, content to hold serve, awaiting an opponent's lapse or a lucky break. They often felt they had too much invested to take unnecessary chances. While a tiebreaker at 6-all would have been even better, this is a start.

5. Angelique Kerber fires coach Wim Fissette

It happened before the WTA Finals, dramatically upping the ante on a growing trend among players to split with coaches regardless of their results. In his one-year tenure, Fissette orchestrated a remarkable revival that saw swooning Kerber reach the Australian Open semis and win Wimbledon. (It was Kerber's third major singles title.) Now he's gone.

Successful coaches are garnering a lot more attention, and their market value has grown considerably. (Neither party ever admits the role money plays in hiring and firing a coach.) As a result, there's more jockeying and negotiating than ever before and more turnover among desirable coaches. Look for coaches to become short-term consultants rather than long-tenured partners as the profession grows in status.

6. Popular chair umpire Mohamed Lahyani gives Nick Kyrgios an unexpected pep talk

During Kyrgios' second-round match at the US Open, Lahyani encourage Kyrgios not to tank. Critics blasted Lahyani for showing favoritism. The USTA called the gesture "beyond protocol." The ATP suspended the well-known umpire for two weeks without pay for trying to pull Kyrgios out of the doldrums.

It's unlikely that Lahyani's momentary lapse of good judgment will have any lasting repercussions. But taken in conjunction with some other incidents that occurred in Flushing Meadows (including Williams' altercation with chair umpire Carlos Ramos) and elsewhere, expect officials to be extra sensitive to how they apply the rules. Their interactions with the players will be scrutinized like never before.

7. The ATP resurrects the World Team Cup

In what looked like a hasty attempt to tap into the newfound popularity of team events -- a gold rush triggered by the Laver Cup competition -- an old event is coming back. Once held on clay in May, the World Team Cup will kick off the new year commencing in 2020 on the hard courts in Australia.

This aggressive move is a major threat to the ITF. The November time slot occupied by the new Davis Cup is unpopular with the top players. The ATP is clearly putting together a viable option that could steal the ITF's thunder now that Davis Cup tradition no longer matters.

8. Line callers eliminated entirely

This came in favor of all-electronic line monitoring at the ATP Nextgen finals, and the players were generally happy with it. Few mourned the loss of that oft-cited "human element."

But don't expect to see all-ELS in the near future. For one thing, it would be prohibitively expensive to wire all the courts, yet using it on one or two main courts would further favor those players who regularly play there. Perhaps more importantly, the challenge system incorporating Hawkeye instant replay is wildly popular with fans and adds an additional strategic element to the game. The lords of tennis will not want to abandon it.