Thomas Tuchel claimed Reece James' development is "far from over" after the right-back signed a new long-term contract with Chelsea.
James has emerged as a key player in Tuchel's Chelsea side since he took over last January, driving forward from a wing-back role or filling in on the right of the German's favoured three-man backline, and has made five Premier League appearances this season.
The England international penned a new five-year contract with the Blues on Monday, which reportedly makes him the highest-paid defender in their history.
Speaking ahead of Chelsea's Champions League opener with Dinamo Zagreb, Tuchel expressed his delight at the Blues' ability to tie down one of their prized assets.
"Of course, he's a very decisive player for us and he's an academy player, and we told you many times how important he is," Tuchel said.
"I think his development is far from over, there's a lot to learn for him and there's a lot to come,
"But of course, we're happy to have a key player with us for so many years."
On the domestic front, Chelsea have claimed 10 points from their first six Premier League outings, which have contained a series of controversial decisions.
Last month, the decision to allow two contentious Tottenham goals in a fiery 2-2 draw at Stamford Bridge led Tuchel to declare referee Anthony Taylor should no longer officiate Chelsea's games, comments which saw him fined by the Football Association (FA).
On Saturday, meanwhile, West Ham had a potential last-gasp equaliser against the Blues denied by a VAR review after a collision between Edouard Mendy and Jarrod Bowen, a decision David Moyes described as "scandalous" as he accused Mendy of feigning injury.
Asked to comment on the plethora of perceived mistakes made in recent weeks, Tuchel asked: "What can I say now to be clear and not pay a fine again? Where is the line?
"Maybe it's better if other people talk about it, our last three home games were like… I don't need that anymore. Red cards, VAR decisions, goals given, decisions not taken where it's obvious to take them.
"Speaking about the last game, I understand the frustration, I understand the discussions about this decision. For me, it's not a 100 per cent decision. It was against Tottenham, it was not now.
"I was happy that the referee got the chance to have a review on the pitch and then it is his decision, we will never have a game without mistakes but at least he gave everyone the feeling that he took the decision.
"I understand the frustration, now it's maybe not on me to comment on it too much but I think the quality of the mistakes, nobody is happy with that."
Pressed on Moyes' comments about Mendy, Tuchel highlighted the FA's refusal to punish the Irons boss, adding: "I did not hear the accusations and you know what happened to me when I spoke about the referee… it was pretty expensive.
"I told you after that I will not comment anymore. I can understand his frustrations, his point of view, and we'll leave it there."
Chelsea have been inconsistent throughout the season's early weeks, and Tuchel believes Tuesday's trip to Zagreb is an ideal opportunity for the Blues to kick-start their campaign.
"We are ourselves in a moment where we need to improve. We are not fully happy with the results," he said.
"We are not fully happy with our performances, so we need to take the next step and it's Champions League so it's very exciting.
"We are very aware of what the challenge is, to play the first match away in a group stage is always difficult, it can always end up in complicated situations, but I think it's very important that we accept it and play a humble match.
"We will accept the challenge and we will accept the fight, and then we can also have the belief and trust that we are able to win, but we need to perform, for sure."