Frank Lampard made six changes to his side for Wednesday's cup clash, which saw Billy Gilmour come in for Mason Mount, and Marc Guehi replaced Fikayo Tomori.
The Blues though were beaten by a fabulous Marcus Rashford free-kick, but Frank Lampard was still very positive of the two youngsters' performances.
"I thought Billy [Gilmour] and Marc Guehi were both really good, Marc was as comfortable as anything," Lampard said post-match to BBC Radio 5 Live
"I’ve come away from tonight – obviously, we don’t want to lose and we know where this is in the competition – but at the same time, there’s lots of positives. In the bigger picture, Marc Guehi’s performance showed that he’s more than comfortable at this level and Billy the same, he was bright.
"It was a tough first half for him because he was trying to get free, trying to be positive and it wasn’t quite happening for him in a way, but I’m really pleased to see them both play so well."
Guehi, 19, was also disappointed with the cup exit, saying it's a 'tough one to take' as the Blues' seven-game winning streak came to an end.
"The defeat is a tough one to take after such a good run of form, but the most important thing is to bounce back and recover and go again in the Premier League," the defender said to the official Chelsea website.
"We played well in spells of the game. At half-time, the manager said to carry on what we were doing, keep moving the ball fast, but with a bit more intensity and a bit more zeal to our game.
"That is what we tried to do and we came out fast and we came out strong. Michy scored a fantastic goal for us but unfortunately, we came away with a loss."
Unfortunately for Marc Guehi and Billy Gilmour, they will now see their first-team chances limited with the FA Cup not getting underway until January.