Christian Pulisic needs to "work daily" to show he deserves to play regularly for Chelsea, manager Frank Lampard has said.
The United States international did not even make the bench for Wednesday's Champions League match at Lille and has struggled to make his mark since moving to Stamford Bridge in the summer.
Pulisic's £58 million transfer from Borussia Dortmund was agreed in January – when Lampard was not manager – but he has not played in the Premier League since August 31 and may not even be selected as a substitute for the Blues' fixture at Southampton on Sunday.
After joining the club for a significant amount of money, more was expected of the American, who turned in an underwhelming display in his recent start against Grimsby in the Carabao Cup.
On Pulisic, Lampard said: "He's level. I spoke to him two days before the Grimsby game and was very clear about the standards and we have to give him the fact he's moved country and moved leagues.
"He's as young as all the young players we keep talking about. He's just turned 21, so I think, if anyone is getting too excited about this, they should calm down because he's started five games for us.
"What he needs to do is work, work daily, work to show within the group that he deserves to play as all the players do, so that's what the focus on everyone is."
Pulisic was not the only high-profile player not involved at Lille, with Ross Barkley not in the 18.
And Lampard added: "This is one of my difficult problems in this job. I have good players and everyone has a story.
"Pulisic has a price tag, Barkley is an international player, Mason Mount is an international player, Callum Hudson-Odoi just signed a new contract, Bayern Munich wanted to buy him last summer and he's an international player.
"Ruben Loftus-Cheek will come back and be an international player. I can't pick them all. All I have to demand of them is that they show me in training and show me they are worthy of the place.
"It's just my job. Next week you might be asking me about two other names. It's the competition that we have."
The return to fitness of Hudson-Odoi has further pushed Pulisic down the pecking order, although the England youngster was recently warned by Lampard.
After the 7-1 win over Grimsby, the Chelsea boss admitted the 21-year-old had areas where "he needs to learn" if he wants to become a regular.
Since then, Hudson-Odoi has been an impact substitute on two occasions for the Blues, setting up goals in the wins over Brighton and Lille.
"I'm really pleased and that has to continue. We can all focus on Pulisic from the other day but Callum's the same and I have to speak in the real world when I speak to them and sometimes as a manager you want more," Lampard said.
"You have to be honest and the players have to react and Callum has now come on with two assists in the games he's come on and that's what you want to keep pushing."
Olivier Giroud is another who has struggled for game-time since Lampard took over at Stamford Bridge, but the Frenchman was praised by the ex-Derby boss.
Lampard added: "My relationship is really good with him. He's a great professional, trains at a level everyday, great in the dressing room and in the game passes on experience.
"Everyone wants to play. I understand that and accept that. I was one of the worst. I hated not playing. I was terrible so on this side of the fence I get it, but all I want to see is positivity, how they are daily in the place and I'm seeing that.
"All good teams need a big squad in these modern days to try and be a successful team and it will need everyone pulling through the season in the same direction whether playing or not and, to be fair to Oli, he's been fantastic and we'll need him."