Diego Simeone praised Joao Felix's fearlessness after the attacker converted a crucial penalty to help Atletico Madrid reach the Champions League knockout stage.
Atletico needed three points to put a last-16 place beyond doubt and did the business with a 2-0 win over Lokomotiv Moscow on Wednesday.
There was an early setback when Kieran Trippier failed to convert a spot-kick in the second minute, his saved attempt piling pressure on a team that had not scored in three games.
But after winning that penalty, Joao Felix took it upon himself to end Atletico's goal drought 15 minutes later.
The 20-year-old Portugal international made no mistake from 12 yards after Rifat Zhemaletdinov's handball gifted the hosts another opportunity to open the scoring.
"He has a lot of enthusiasm, a lot of optimism and he is young," Atletico head coach Simeone told Movistar when asked about Joao Felix after full-time.
"When you are young, you are not afraid of anything. Joao is going through that stage. He played an important game.
"Joao continues to grow, has a lot of things, [but] we need the strikers to combine better and find that last pass to finish games earlier."
Joao Felix's goal was his second in Europe for the Rojiblancos and first in any competition since their victory against Lokomotiv in October.
"My father has always told me not to be afraid of taking responsibility," he said. "I have always liked to convert and that is what I did."
Atletico were made to wait until the 54th minute before centre-back Felipe supplied the sealer.
Simeone's men finished Group D with a four-point buffer to Bayer Leverkusen, who lost 2-0 at home to table-toppers Juventus.
Speaking about his team's four-match winless run, Simon said: "It was a moment with pressure after the previous results, but with [Trippier's] failed penalty there was not a drop of negativity in the environment.
"The players noticed it. They attacked well on both sides, with Joao at an important level. I'm happy, because it isn't easy to reach the Champions League last 16."
The draw for the next round will be made on Monday.