He returns to the Australian Open, where he lost a thrilling five-set final to long-time rival Roger Federer in 2017, after overcoming his chronic knee problems just in time and hoping to continue last year's progress under new coach Carlos Moya.
That is giving Djokovic some hope. Throughout the tournament, I don't know how it's going to behave. "Who would predict that after his six months of absence, so. everything is possible really".
Del Potro has not played in Melbourne for four years because of his injury troubles but heads back with his status as a Grand Slam contender restored by his memorable run to the US Open semi-finals. "Even if it's 100 percent healed, after six months of no competition, you never know how you're going to react", the 30-year-old added.
Rafael Nadal gearing up for Australian Open
"So hopefully I can improve that".
Agassi had to modify his own service motion because of a wrist injury in his career and he had input into the redesign for Djokovic.
"Both Radek and Andre ... they spent a lot of hours analysing my serve".
"We've talked about that", Djokovic said.More news: Southern California mudflows triggered by fire and rain, with more possible
Injuries to leading players have been a focus of attention in Australia.
The Bulgarian came agonisingly close to beating Rafael Nadal in the semi-finals in Melbourne when he went down in a five-set humdinger, but finished the season ranked third after winning the biggest title of his career at the ATP Finals in London.
In recent months, meanwhile, ATP Finals victor Grigor Dimitrov and Zverev have moved up to No. 3 and No. 4 in the rankings, respectively, and are growing in confidence that they're on the cusp of Grand Slam breakthroughs.
"I've showed on multiple occasions over the year that I can play and beat the best guys in the world", Zverev said.More news: Bautista Agut edges Del Potro in Auckland final
"I had a great year on tour but the grand slams have been a little bit shaky for me still".
There may be no Andy Murray, but the men's tournament will have no shortage of returning stars who will all be aiming to start 2018 by claiming the Australian Open title.
"The correction and improvements to the serve are allowing me to be more efficient and spend less energy", he said.More news: Jacksonville Jaguars: How Blake Bortles compares to Super Bowl QBs
"So let's see. There's not much more I can do".