LONDON -- Christian Pulisic's arrival at Chelsea next summer is not a threat to Callum Hudson-Odoi's chances of a first-team breakthrough if he stays at Stamford Bridge, said assistant coach Gianfranco Zola.

Chelsea confirmed on Wednesday that they had agreed a €64 million deal with Borussia Dortmund to sign Pulisic, who will spend the rest of the season in the Bundesliga before joining his new club.

The move has raised further questions about Chelsea's desire to develop Hudson-Odoi, who has made just six appearances in all competitions this season and is holding off signing a contract extension amid serious interest from German giants Bayern Munich.

"Pulisic coming here ... he is a player that has done very well and we're very happy to welcome him and the club is investing for the future," Zola said. "We have players that have a certain age and we are thinking about the future. This shouldn't be a problem to Callum.

"You can see recently that we played with three small players up front, so we played with Eden [Hazard] up front and actually the team did very well with the system, so it's leaving another space on the wide areas. Pulisic is coming because the club is moving for the future but we believe that he [Hudson-Odoi] is in our future as well."

Zola urged Hudson-Odoi to show patience in his development at Chelsea in a news conference on Friday, and the Italian warned that the winger will not find first-team minutes any easier to come by at Bayern if he leaves.

"He has to think long-term," Zola said of Hudson-Odoi. "I know it's very difficult when you are young. You think about what is going to happen tomorrow, but you have to be thinking after.

"We have two players, they are very good players but both of them are over 30 -- Pedro and Willian. We value them, of course, we value them a lot but we know there will be a moment in which probably Callum is going to come and Callum is going to overtake them so it's important that you think about this.

"You stay here, you have already started a process in which you have to probably wait a little bit but I wouldn't say even too long. Or the alternative is to go somewhere [else]. You go somewhere and it's going to be the same.

"You will have to start again. Do you think that you go to a big team and you are going to go straight into the team? It doesn't work that way. So that's all I think. And when I say this I am genuinely talking about the best for the player, not the best only for the club."

Chelsea's task in convincing Hudson-Odoi to sign a new deal has been made harder by the meteoric rise of Jason Sancho at Borussia Dortmund, coupled with the regular minutes that former Arsenal loanee Reiss Nelson has been afforded at Hoffenheim.

"Probably he saw the way it went for them," Zola admitted. "But again I think he has to realise this coach [Sarri] likes to work with the young players and he improves them day by day, so I think Borussia Dortmund for Sancho for him could be here.

"I do believe in this. In here he can improve and we are going to spend time to make him better and I am sure if he stays here he will play games."

Another player facing an uncertain future at Chelsea is Alvaro Morata, who has struggled on and off the pitch to shoulder the burden of expectation since moving to Stamford Bridge from Real Madrid in the summer of 2017.

Zola, however, was brutally honest in his assessment of the Spaniard's situation: "It should be a motivational thing. You are at Chelsea, you're not playing for Southampton, or Brighton, with all due respect for those clubs.

"People, they expect a lot from the No. 9 of Chelsea, they expect a lot of goals and a lot of performances. This is normal and Alvaro has to get used to it.

"If he goes to another big club it's going to be the same. There is no way you can avoid your responsibilities, it's part of your job and the better you can handle those situations the better you're going to be."