Alvaro Morata has "great potential" but he needs to work on his mental strength, according to Chelsea head coach Maurizio Sarri.
Morata scored twice in Sunday's 3-1 Premier League win at home to Crystal Palace, sending the Blues up to second place in the table.
The 26-year-old has now scored four goals in four Premier League appearances having regained his confidence following a back injury and loss of form last term.
But Sarri feels there could still be a lot more to come from the striker, who lost his place in the Spain squad as a result of his 2017-18 struggles.
"Alvaro improved [in] the last month," Sarri told a news conference. "Improved for the confidence, improved for the personality, improved also from the technical point of view.
"Now he's able to play more with the team, I think. But I think, also, that Alvaro has a very great physical and technical potential, so I think he can improve more.
"For Alvaro, the goal has to be a consequence. He has to play for the team, with his mates, without thinking about goals. Goals are usually a consequence of teamwork.
"He's a little bit fragile. From the mental point of view. But he's very young. I think he can improve, improve very fast."
Sarri, though, rejected a suggestion Morata could develop into a similar striker to club great Didier Drogba, who scored the winning penalty to earn the Blues the Champions League title in 2012.
"Physically, no. But Drogba was one of the best in the world for 15 years," he added. "But Alvaro is very fast.
"Not in the first two or three steps, but if he has to run for 40 metres he's very fast. He's strong, so not like Drogba. He has great potential."
Chelsea were grateful to Eden Hazard for his impact off the bench, the forward winning a free-kick that he delivered for Morata to restore their lead within two minutes of his introduction.
"Very important. Today it was very important to have him on the bench," Sarri said of the Belgium star. "I spoke yesterday with the doctor and he said he was doing better but, for me, he is not able to play for 90 minutes.
"So I asked for the bench, and he said I could try. But no more than 30 minutes. We were lucky. Immediately, the first minute, I think, he was able to change our match. But you know, Hazard is Hazard. He's able to do this very often."