The Novak Djokovic rebuilding process far from complete

Before Novak Djokovic could entertain the idea of returning to top form, the 12-time Grand Slam champion ended 2017 by withdrawing from an exhibition in Abu Dhabi.

It was a fitting end for a player who is coming off the most disastrous year of his storied career. The last competitive match Djokovic played came at Wimbledon this past July. He was facing Tomas Berdych in the quarterfinals, and after losing the first set, Djokovic hit a sloppy forehand wide in the second, then walked toward the net, shaking his head in frustration.

That was it. His season was over.

He officially made the decision two weeks later, in late July, saying the pain in his right elbow that had bothered him for some 18 months had grown to be too much. The US Open in late summer marked the first Grand Slam he had missed in more than 12 years, a streak of 51 majors played in a row snapped, dating back to the Australian Open in 2005.

But Djokovic is back in Melbourne to start the season. He has added the recently retired Czech player Radek Stepanek to his coaching team and has retained the services of the legendary Andre Agassi as a coach and adviser. Djokovic and Agassi linked up last spring before the French Open after the Serb split with his longtime entourage, including coach Boris Becker.

Coming into 2018, if Djokovic's elbow (and other Gumby-like body parts) stays healthy, Agassi has sky-high expectations.

"I want him getting better," Agassi told ESPN.com in an interview in November. "He can win without me. He's proven that, but we want him to have the same [kind of] success again. If he doesn't make changes both emotionally and mentally, he's going to run into the same intensities that led to his fall from being so dominant in the first place.

"You can't afford to do that in your 30s. You have to figure out new solutions for new problems. I think that's where I have a lot of experience to help him make life a little easier."

The Australian Open is the tournament where a reborn Agassi was as lethal as ever in the latter stages of his career. He won titles inside Rod Laver Arena in 2000, 2001 and 2003, which marked the final three major trophies of the eight that he won in his career. He was 29, 30 and 32 during those championship runs.

Djokovic will turn 31 in May. He has won in Melbourne six times himself.

It's Djokovic's fitness that has brought him to such great heights, most notably a run from the summer of 2014 through to the French Open in 2016, where he won six of the eight Grand Slams he played in, including four in a row.

But then something snapped. Djokovic has never gone into detail, but he said that he was dealing with "private issues" during Wimbledon in 2016 when he suffered his shocking loss to Sam Querrey. Djokovic hasn't won a major since, and at the French Open this past spring, he was humbled by Dominic Thiem in the quarterfinals, with some questioning his effort in the third set, which he lost 6-0.

It is that time away -- six months nearly to the day come the start of the Australian Open -- that the now world No. 14 hopes has refreshed him mentally and physically. He is an athlete who relies on his body perhaps more than any other in this sport.

"His game is certainly tied to his fitness," said former touring pro Leif Shiras. "The level of fitness is higher on tour all the way around, and Novak has this willingness to go one shot deeper in the rally, to use his legs. That is going to be important for him: Can he be healthy? He's not like [Roger] Federer, who can attack at will. He lets the point develop a bit. It demands a pretty high level of sophistication."

Federer's choice to cut off his season in 2016 at the halftime mark because of lingering injuries looked like the ultimate sophisticated decision. He came back better than ever in 2017, winning in Australia and then at Wimbledon for a previously unfathomable eighth crown there.

Djokovic followed suit this past year, as did Stan Wawrinka, Milos Raonic, Kei Nishikori and Andy Murray, all shutting their seasons down early, all hoping to right their bodies for the 2018 season. The time away worked for Federer, but he's also done things no other player in history has done. Can Djokovic emulate one of his biggest rivals?

"You can play as many practice matches as you want and drill yourself into fitness, but the match fitness -- you have that nervous energy -- your fatigue levels can change," Shiras noted. "How does your body react to that? Put yourself in the heat of battle, and your body can respond differently. We'll see how he does."

Agassi, who was reported to be in a snowboarding accident last month, is expected to be in Melbourne after doubt of his attendance at the year's first major. He's a powerful -- if unorthodox -- figure in Djokovic'a corner.

"It's not a job for me, so I'm going to do my best to help him in an achievable way," Agassi said. "It's not the same as coaching a 19-year-old. He's won more than I have. I just have to make sure I give him that little bit that helped me overachieve. Because he's just so gifted in so many ways that he doesn't realize how much easier it still can be for him."

The Djokovic team did all spend time together in Monte Carlo, where he lives, in the preseason, with Agassi and Stepanek side-by-side, joined by strategist Craig O'Shannessy, who has worked with Djokovic for a year now.

In his comeback, O'Shannessy says, don't expect to see much different from Djokovic, at least from a game plan point of view: He still will be the gritty, try-and-hit-it-past-me brick wall he has been at the top of the tour for much of the past 10 years.

"He's still going to be that guy on the baseline looking for the short ball and the chance to move in," O'Shannessy told ESPN.com. "His game is about a pattern of play where he can move his opponent around and then look for his opening. He's built his career on that. I don't think you're going to see that change much."

What tennis fans don't know is what they will see, in fact, from Djokovic in 2018. The first half of 2017 was full of uncharacteristic losses, including setbacks against unheralded Denis Istomin in the second round of the Australian Open, twice to Nick Kyrgios, a blown lead against David Goffin on clay and then that Parisian head-scratcher versus Thiem at Roland Garros.

"He's got 12 majors. That kind of number is certainly going to bring a level of confidence, but a lot of personal expectation too," Shiras said. "For elite players, it's all about their mental state. Champions are tested in different ways, and it's going to be a new test for him.

"It's a comeback challenge. Roger faced those impressively. [Rafael] Nadal has faced them in the past. And now it's Novak's turn. It's part of the process if you want a prolonged career. This is when the injuries are going to have their most impact. How does he manage that?"

That's partly Agassi's role, and now the ultimate question of Djokovic himself heading into this season. Agassi mentioned a subtle yet important concern: how Djokovic deals with adversity. His game has been built on a physicality that was unseen before, held up only by that mental fortitude of a champion that oftentimes comes only once in a generation. Whatever he's worked on in his time away was more of the mental side -- and now the ultimate challenge to stay healthy.

Settled into his 30s, can Djokovic sustain that? That's what Melbourne and beyond will help us understand. Or at least try to.