Frank Lampard has offered an explanation for the "tough" decision he took to leave Callum Hudson-Odoi out of Chelsea's draw with Tottenham.
Hudson-Odoi scored his third goal of the season for Chelsea against Rennes after being handed a rare start in the Champions League last week.
The 20-year-old's cool finish set the Blues on their way to a 2-1 victory which saw them qualify for the round of 16, but he was subsequently dropped for a heavyweight Premier League clash against Spurs on Sunday.
Lampard did not include the England international in his final 18-man squad for the London derby as he restored Hakim Ziyech to his starting line-up to play alongside Timo Werner and Tammy Abraham in a front three.
Chelsea ultimately missed the chance to move top of the table after being held to a 0-0 draw by Tottenham, who are ahead of reigning champions Liverpool on goal difference.
Lampard insists Hudson-Odoi's omission was nothing to do with his recent performance levels, and has urged him to keep his head up and continue working hard behind the scenes in order to fulfil his potential, with his next chance to shine likely to come in a midweek trip to Sevilla.
"It was difficult. I have been pleased about his training recently. His attitude in training at the minute is bang on," Lampard told a press conference of the winger's current standing in the squad.
"That work ethic in training is effective in him scoring against Rennes and playing well, coming on against Newcastle and he was bright after going away with the Under-21s and doing well.
"It was tough. I have tough decisions when I have a fully-fit squad, as we pretty much do now, to leave out players that work hard through the week and are desperate to play for the club.
"I did speak to him personally. I want him to understand where he is at the minute, which is in a progression that's getting better. There will be times where others players have to sit out and that's a conversation we have to have with other players.
"He is in contention for tomorrow and I want to see more of the same and keep that progression going. Like I say, if there are times where he is out of the squad, I want him to stay positive. That's part of my job as well to have that communication level."
Lampard added: "For all these players you are talking about, in my squad, I have to leave out four or five players per game. If I speak about all the permutations of all of them and considered the risk of it then I wouldn't be able to make a decision or do the job.
"I am aware of Callum and where he is at. He took it very well and it is not an easy conversation to have because all players want to play, I expect that. He will get his opportunities.
"He will get minutes tomorrow. It is up to him then to show when he plays that he deserves to start because there is competition in that area. That's the reality of playing for Chelsea.
"At the same time, if I feel like I am taking someone out of the squad when they deserve to be in it, I have to be straight and honest with them to try and keep them positive and working in the right direction.
"Hopefully with Callum, I have got that. His reaction was great and since the game, and in training today, he has been great and it will show when he plays."
Asked if he endured the same struggles as Hudson-Odoi at the start of his own playing career, Lampard responded: "Yes, I can relate to that as we all have steps on the ladder. I think Callum's early career, he got into the team with a lot of talk around him in the year before I came.
"Then he got a really bad injury and a big part of last season, even this season, he was feeling the injury a little bit. I think now time and work is showing he's back with his recent form to where we want him to be.
"At the same time, he is still a developing player because when there's a lot of talk about a player then you think they have been around longer than they have. He is still a young man so unfortunately for him, I have to see the bigger picture.
"It is unfortunate he is not part of the squad but there's hundreds of games ahead of him and progressions to make. He will have a big impact with his talent, as long as he has that hard work, which he is showing at the minute."