Chelsea's Christian Pulisic was left out of the squad entirely when they beat Lille in the Champions League earlier this month, but the 21-year-old's career sprang to life against Ajax Amsterdam on Wednesday.
The forward joined Chelsea from Borussia Dortmund for a fee of around €64 million in the close season to become the most expensive American player in history but has struggled for minutes, making only three Premier League starts.
Pulisic gave manager Frank Lampard a timely reminder of his talent by setting up fellow substitute Michy Batshuayi to score the winner in Chelsea's 1-0 triumph over last year's semifinalists Ajax at the Johan Cruijff Arena.
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"Sometimes the toughest part of management is leaving out players that really want to play week in, week out. You rely on them being positive and coming on to make an impact," Lampard told reporters.
"You have to give Christian huge credit because he looked so lively and the assist is just as important as the finish."
Pulisic had admitted to being frustrated by limited playing time, with the media speculating that he could leave Chelsea on loan during the January transfer window.
"I've tried to shut my ears to a lot of the outside talk ... I understand his quality, his young age and the fact that it's a big move for him," Lampard said.
"He wants to know what I want from him, what the Premier League is like and that's not always an easy ride but we've stayed calm and kept looking at the big picture."
Lampard said the result, which left Chelsea with six points after three games in Group H, had set the benchmark for his youthful side.
"It feels huge. That always scares me because there's a lot to do and it's just six points halfway through the group now, but we're entitled to be excited," he said.
"It can be a bit of a blueprint for us in terms of the work from the midfield players which was outstanding ... but there's no excuses for us now to dip from that.
"The younger players are still babies in Champions League minutes, so this was a huge test ... but the balance of our team between young players ... and experienced players who they rely on to set examples was good."