LONDON -- Eden Hazard must work harder in training if he wants to be the world's best player and Chelsea have only seen "75, 80, 85 percent" of his potential so far, according to head coach Maurizio Sarri.
The Belgium international is off to a blistering start to the season after scoring seven goals in his first eight appearances for club and country in all competitions, including a spectacular solo strike to eliminate Liverpool from the Carabao Cup in Wednesday's third round tie at Anfield.
Such displays have led many to suggest that he is ascending to the level of Lionel Messi and Cristiano Ronaldo. Sarri believes Hazard is a "genius" and wants him to get there, but insisted that his improvement must begin every day at Cobham.
"I think that he is for sure one of the best [in the world]," Sarri said. "But I am absolutely convinced that he can improve.
"If he's able to improve during the training, maybe he will be able to use himself at 100 percent because, I think that we have seen only 75, 80, 85 percent of his potential. I think that if he is able to improve, he will be the best in the world."
Asked how Hazard can improve, the Italian replied: "For example, with more intensity in training. I think [if he does that, he could be voted the best in the world]. It's very difficult to compare him with other players. He is a genius, I think. It's very difficult. He's unique."
Sarri was at pains to stress that he is not questioning Hazard's level of commitment to training, but added: "[I want] more continuity. From the physical point of view, from the mental point of view, because I think he has the opportunity to improve more. He can become the best player in the world.
"He's a genius. Technically, I think, he is the best. And so I want him to be the best in the world. It's a very interesting challenge [for me], I think. He has a lot to give. A lot to give to himself, to the team, to the staff. And I want everything."
Hazard's dazzling form has further strengthened his hand in any future contract talks with Chelsea, who are desperate to tie him down to a long-term extension.
The Belgian told Gazzetta dello Sport on Friday that there is "no news" regarding contract discussions. Sources have told ESPN FC that Chelsea are prepared to make him the highest-paid player in the club's history as part of any extension, but Real Madrid remain long-term admirers.
Hazard did offer Chelsea encouragement in their hopes of keeping him around for the long term, however, by delivering an emphatic endorsement of Sarri as well as summer arrivals Jorginho and Mateo Kovacic, who have completely transformed the team's style of play.
"You can see it on the field -- we've got new players, people who love possession of the ball," Hazard said. "We have more possession than in the past and the forwards are benefitting from this new philosophy.
"Sarri knows how to get the best out of us, clearly. I don't want to be disrespectful to Roberto Martinez, but when his time as Belgium coach is over, Belgium could consider Sarri to replace him. I think his results are excellent."
The visit of Liverpool to Stamford Bridge on Saturday will provide more clarity on the seriousness of Chelsea's title aspirations. Sarri has consistently played down his team's chances of lifting the Premier League trophy this season, but he is far more confident that Jurgen Klopp's men possess the requisite quality.
"He is one of the best coaches in the world at the moment," Sarri said of Klopp. "[Liverpool] have worked very well in the last season with these players. Now I think they are ready to win. Maybe the Premier League, maybe the Champions League. But ready to win something important."
Antonio Rudiger (muscle problem) and Pedro Rodriguez (shoulder) are Sarri's main injury concerns ahead of the Liverpool game. Both men participated in the second training session on Thursday afternoon, but Chelsea will leave a final decision on their fitness until closer to kick-off on Saturday.
Looking beyond Liverpool, Sarri said he should be able to reveal his captain choice next week after talks with his squad and the club; Cesar Azpilicueta and Gary Cahill are the only players to wear the armband for Chelsea this season, and the Italian would not be drawn on whether or not Hazard is a candidate.
Sarri also said he considers it a priority to find out why Chelsea's performance levels fluctuated so wildly under Mourinho and Conte. The Blues followed Premier League title triumphs in 2014-15 and 2016-17 with 10th and fifth-places finishes, respectively.
"The history of this club is a little bit strange," Sarri admitted. "[In the 2014-15 season] I think 87 points. [In 2015-16] 50 points. That's very strange, with the same coach and the same group. Then 93 points [in the 2016-17 season] then 70 points last season with the same coach and group.
"I need to understand why. I am studying. I think that these numbers tell us something. I don't know what, at the moment. But I want to understand and I want to help my players to be at the same level."
Asked if the problem could be more to do with attitude than skill, Sarri replied: "I don't know, because they usually have training very well with continuity. So the attitude is good. There is probably something from the mental point of view. I have to understand it."