Conor Gallagher was the toast of the stands after opening his Atletico Madrid account in a 3-0 win over Valencia on Sunday evening.
Fans draped in red and white waved their flags and chanted Gallagher's name after the former Chelsea star opened the scoring in the first half.
It was a neat finish from inside the area, Gallagher sliding the ball past an onrushing Jan Oblak after being played in by midfield team-mate Rodrigo De Paul.
The victory means Atletico are second in LaLiga and still unbeaten after five games, with Gallagher having won all three of his matches so far.
He will get his first taste of the Madrid derby later this month when Real visit the Metropolitano, setting up a clash with fellow England star Jude Bellingham.
In a protracted saga, his transfer initially stalled after he agreed personal terms when the Blues' move for Atletico's Samu Omorodion fell apart.
Gallagher returned to Cobham to train on his own and nervously wait to see if the deal would conclude.
Atletico teased the signing online with a bizarre graphic of a pitbull - seemingly a reference to a section of Chelsea's support calling Gallagher a dog for his willingness to press and win the ball.
Many see the union of Gallagher with manager Diego Simeone as a perfect stylistic match.
In scoring against Valencia, the midfielder also scooped up the obscure honour of being the third-youngest Englishman to score in LaLiga this century.
Only Jude Bellingham and Mason Greenwood have scored at a younger age in LaLiga in the 2000s.