Thomas Tuchel has challenged Callum Hudson-Odoi to have the same impact from the bench as he does when starting games for Chelsea, though insists there is no issue between the pair.
Hudson-Odoi came on as a substitute at the start of the second half as the Blues trailed 1-0 at Southampton on Saturday, only to then be taken off himself as he made way for Hakim Ziyech in the 76th minute.
Mason Mount's penalty pulled the Blues level at St Mary's Stadium, but the decision taken by Tuchel to replace the replacement was the major talking point from a game that finished 1-1.
The former Paris Saint-Germain and Borussia Dortmund coach explained the England international was not "sharp enough" during his time on the pitch, but was his criticism fair? Even Tuchel admitted afterwards that it may have been an unfair call.
"You cannot play at 99 per cent, it's not possible. You play in the Premier League, and it's our standard to ourselves, to be 100 per cent sharp," Tuchel told the media.
"I did not feel it with Callum. Maybe it's unfair, maybe I misjudged him. But it was my feeling on the sideline when he played close to me.
"I did not feel him sharp enough, did not feel he was really into this game like everyone else.
"I took a hard decision on him, yes, but it is the decision for today, for the game. There is no need to worry for him, I trust him a lot.
"He has had some very, very good games, both mentality wise and in terms of effort when he started, two not-so-good games when he came on from the bench. Let's improve together."
Hudson-Odoi did have a limited impact on proceedings when sent on against Southampton, completing seven of his 10 attempted passes while failing to create a chance or take a shot during his brief outing.
The 20-year-old has started five of Tuchel's seven games in all competitions and starred in the home win over Burnley in particular, setting up a goal and creating four chances in total.
While not quite able to provide the same threat in the following game, when he featured for just over an hour at Tottenham, Hudson-Odoi did seem to make a difference when coming on as a sub in the 2-1 triumph over Sheffield United, laying on two opportunities as he completed all 13 of his attempted passes during a 28-minute cameo.
Still, Tuchel clearly wants more consistency when utilising Hudson-Odoi from the bench, though made clear what happened on Saturday will have an impact on the player in the future.
"It's absolutely not a big thing for me, and hopefully not for Callum," Tuchel said. "I talked to him and talked to the whole group, this is sometimes possible and not a big thing.
"If you want to make it that, and people want to talk like it's a big thing, then it's like that, but for me it's not a big thing.
"It's on Callum to show that he's a reliable guy from the bench, like he is when he starts – and he starts a lot.
"You cannot even create the slightest cut between me and Callum. It takes a hard decision; swallow it, then be there for tomorrow when you have all chance to start against Atletico."
Chelsea face a tough run of fixtures in the coming weeks, starting with Atletico Madrid in the first leg of their last-16 Champions League tie.
They then host Manchester United in league action at Stamford Bridge next Sunday, followed by a trip to Anfield to take on struggling champions Liverpool on March 4.