The manager didn't use the £58 million signing from Borussia Dortmund at all in the Premier League in September, with Chelsea preparing to face Southampton on Sunday in their first October league match.
Leading up to the game, Lampard explained why Pulisic continues to not be selected ahead of the likes of Willian, Mason Mount, Pedro and the returning Callum Hudson-Odoi.
"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 that he’s moved country and moved leagues," Lampard told reporters at Cobham Training Centre.
"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 and what he needs to do is work, work daily, work to show within the group that he deserves to play.
"As they all do, as all the players do. That’s what the focus on everyone is. This is one of my difficult problems in this job. I have good players and everyone has a story.
"Christian Pulisic has a price tag. Ross 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. He’s an international player.
"Ruben Loftus-Cheek will come back and be an international player. I can't pick them all and be in the game unfortunately. All I have to demand of them is that they show me in training and show me that they are worthy of the place.
"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.
"You have to be honest and the players have to react to that and Callum has now come on with two assists in the games that he’s come on and that’s what you want to keep pushing. I love the young players. I particularly love the young players because I want them to improve daily.
"At the same time, sometimes I have to make harsh decisions and say something that I see can help their game but might not sound that nice because I want them to be the best, all of them. That’s what I want them to be. That’s part of the process."
Pulisic isn't the only player struggling for minutes after Chelsea switched managers again this summer from Maurizio Sarri to Lampard. Ross Barkley was left out of the squad along with Pulisic on Wednesday night, while Olivier Giroud is struggling to get on the pitch with Tammy Abraham having now scored eight goals this season.
France manager Didier Deschamps joked about Giroud's lack of minutes earlier this week, with the striker still pivotal to his squad. Lampard was keen to state that he is keeping Giroud in his plans, despite the striker currently being on the fringes of his squad.
"My relationship is really good with him. He’s a great professional, trains at a level every day, great in the dressing room and in the game, he passes on experience," Lampard said of Giroud.
"But in terms of that, everybody keeps asking me about the players that aren’t playing but it’s a difficult one because some players can't play whether they’re 32 or at the other end of the spectrum at 21.
"They have to keep working and be positive within the group because I’ve got no winners in this game, I want the club to win. So when I choose to select people or not it’s because I think it’s the best thing. I’m not blind to the fact when you’re not playing, it’s not nice.
"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, I get it, but all I want to see is positivity, how they are daily in the place and I see that.
"I see that and that’s sometimes the thing people in the outside world doesn’t see - why is he not playing? This one or that one. I’ve got to make choices in training and I want the group to be positive and well spirited and getting results, and at the moment we are doing that and it has to continue, because like all good teams, we 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.
"To be fair to Oli, he’s been fantastic training and we’ll need him. Tammy has scored a lot of goals, scoring regularly, which is great for us. But Tammy needs to know that if his level drops you’ve got Giroud and (Michy) Batshuayi training well and trying to get into the first team. That’s the competitive nature of the squad, that’s what we’ve got and what we want."