The Stamford Bridge boss has moved to throw his backing behind Mount, James and Gilmour, however, pledging Sunday's showing will not affect his long-term thinking.

"Mason wouldn't have been happy to come off at half-time," said Lampard.

"I know that from myself and, if there's one comparison I can make, it is that I know if he's not playing then he won't be happy and if he comes off he won't be happy.

"But it was certainly a moment that he should not be happy that evening and then get straight back to it afterwards, because he knows how much I trust in him and he works brilliantly every day.

"And when I say Mason, I mean Billy (Gilmour) and Reece (James) in the same breath because they show similar attitude.

"There will be no problem, no problem with Mason because it was a one-off game, I had to make a decision and it doesn't affect my thinking for West Ham or going forwards.

"Mason played 90 minutes in both the first two games after the restart, and was unfortunate not to score or have an assist. So he had two big performances in a week.

"And then with the Leicester game Mason didn't have a bad performance, it was just a performance in line with the team and my choices to change were more about the players I could bring into that performance as opposed to the ones that were on the pitch.

"I could make a lot of changes in that game, so it was more about, 'Can I bring some energy into the team?'

"So I rely on Mason a lot, I did at Derby, I do at Chelsea, he brings so much to the team in his work ethic and the way he can start the press in midfield.

"His quality on the ball is already at a high level and it's only going to get better."

Mount broke lockdown rules in March to enjoy a public kick-about with close friend and West Ham star Declan Rice. Lampard admitted he spoke briefly to Mount, with the 21-year-old very quickly aware of his error.

Mount and Rice will come face to face as Chelsea take on West Ham on Wednesday night, with Lampard challenging the Portsmouth-born midfielder to shine in the battle for bragging rights among mates.

"I had the shortest word possible because I saw Mason a couple of places get compared to players who went out and partied, stayed out all night and did different things," said Lampard.

"I'm not wanting to angle on that one, but what I wanted to say on Mason was (he) very innocently, and naively, and wrongly at the time (broke lockdown rules) and he very much quickly held his hands up to that.

"But he was kicking a ball about and that's so typical of Mason and how he lives his life. So I had the shortest ever conversation with Mason – he was very apologetic and said he got it wrong straight away and we moved on. No problem at all.

"I think it spurs you on more if you have a personal relationship with an opponent either way – whether you are best friends or you don't even like each other.

"I also think the result of that is not concrete either – you will either have your best of games in that sort of circumstance but you can also become overly focused on that relationship and have a not so good game.

"They are two very good players. But there is only one thing I will ask of Mason – and from my point of view that is obviously all I care about going into this one. He texts him tonight, he smiles at him in the tunnel or whatever it is, but if and when they go up against each other he has try to beat him in every individual battle that he possibly can.

"And sensing Declan Rice's character, I am sensing they will both be like-minded on that one. We will see."