Michael Ballack has urged Kai Havertz to continue his development at Bayer Leverkusen despite growing speculation over a summer move to Bayern Munich.
Last season, the 20-year-old enjoyed a sensational breakout campaign, scoring 20 goals and registering seven assists, earning himself a call up to the Germany squad.
He has struggled to recapture that form this season, although interest is said to still be high from Bayern, who are reportedly looking to rebuild their squad this summer.
"If Bayern act in perspective and you still want to get the best German players, Havertz has to be brought in," former Bayern and Leverkusen midfielder Ballack told Sport1.
"He is an exceptional player, but one thing is also clear... Havertz still needs time.
"He also needs the robustness to be mentally prepared for Bayern. I also needed my time in Leverkusen back then.
"Havertz must now look closely at his development. We do not need to talk about his footballing qualities because he is a top player.
"Bayern have to decide whether they need his role and what he is worth to them. He is sure to bring everything Bayern needs.
"But the possible transfer must also fit into the financial framework."
Sky Sports News reported in December that Havertz was expected to stay at Leverkusen for the remainder of the current campaign.
Chelsea, Liverpool, Manchester United and Tottenham are among the clubs understood to have been monitoring Havertz.
But Ballack added: "He is still in the development phase and has mistakes in his game. But that's normal too.
"He is currently in good hands in Leverkusen. There he can develop his personality in peace.
"At Bayern you need other characteristics to assert yourself. Just being good is not enough there."
'Havertz could go for as much as £100m'
German football expert Raphael Honigstein believes Havertz will leave Leverkusen this summer and says he could go for as much as £100m.
"The summer move is more of just a given, he perhaps would have been happy moving last summer," said Honigstein, speaking on the Transfer Talk podcast.
"There was interest there but Leverkusen made it very clear he wouldn't be allowed to leave and I think he ultimately thought it wouldn't be the worst thing to spend one more year there.
"Leverkusen know that this is a situation that won't be able to continue - he has basically outgrown this team already and he will certainly move in the summer.
"The valuation will not be significantly lower than it was last summer, which was well north of €100m, maybe even £100m, that sort of price range. I think Leverkusen will get the money solely because so many clubs want him."