Mauricio Pochettino says Noni Madueke channelled his frustration in the right way to prove a point to his manager and the rest of the squad.
The 21-year-old winger sent Dean Henderson the wrong way from the penalty spot with a high-pressure 89th-minute spot-kick which he won himself, to secure a 2-1 win over Crystal Palace.
Madueke has been a fringe player this season, playing just 232 minutes all season, and was dropped earlier in the season after being filmed in a nightclub during an international break.
However, Madueke was outstanding in his 20-minute cameo and earned praise from his manager.
"He plays free - the difference is, he did what we needed in this moment," Pochettino said when asked by Standard Sport.
"He went to play and I liked it because he showed he was upset with me. Okay, sometimes he has been injured, but I think, yes, [he thought] 'I am now going to show the coach that he can trust me'.
The Chelsea boss added: "It was private [what I said to him after the match] but I think we were talking in this way [about proving a point].
"They need to show me that I can trust and mentality is really important, more in this football that is the Premier League, you can not only play with quality.
"Of course, you need quality but if you don't have the right mentality and approach every single day in training and the games then it is difficult to perform. If you have a young team, performing is about not thinking and fighting for yourself and the team.
"It was so nice to receive this energy in the game when we decided to include him on the pitch and then at the end of the game.
"It is about this being the way he needs to behave every day. It is not about us being bad people and not wanting to play with some people - because he has quality - and it is a shame to go there and not show the quality or mentality.
"You can only show your talent if you show the right mentality."
The inhibition and confidence showed by Madueke was in stark contrast to many of his team-mates, who made errors in a nervy London derby.
Pochettino admitted the personality shown in Madueke was not apparent in all of the Chelsea players, as they struggled to victory after Michael Olise equalised just before half-time, with Mykhailo Mudryk opening the scoring.
"We didn't start well," Pochettino said. "We were a little bit nervous and didn't manage maybe the pressure to play a game that was really important for us - we needed to win.
"A young team like us maybe were struggling because we were thinking too much. I told them at half-time to stop thinking because when they think, the ball is always going to be late when they circulate the ball and find the space.
"We moved the ball so slow from the beginning but we had chances to score and we scored one goal. But I wasn't so happy, and when we conceded in the last minute, it was a massive impact when starting the second half.
"I think we played a little bit more in the second half, and I was so happy that the players from the bench had a good impact on the team that we wanted to be consistent."
He added: "It was as if they felt they were going to fail and crash and you feel like you can do nothing from the touchline and you cannot help."
