Cole Palmer was ruled out of Chelsea's Premier League win over West Ham at the London Stadium on Friday after suffering an injury during the warm-up.
The England international was replaced in Chelsea's starting lineup by Brazilian teenager Estêvão as Chelsea went on to win 5-1 over their London rivals.
After leaving the warm-up early and walking down the tunnel, Palmer took a seat on the Chelsea bench as the game kicked off.
Speaking after the game, Chelsea manager Enzo Maresca said Palmer had been taken out of the team as a precaution.
"In the last four or five days he was not 100 percent and tonight in the warmup he felt again something so we prefer to not start with him, not take any risk to make it worse," he told Sky Sports. "We'll see in the next hours [how he is]."
In Palmer's place, 18-year-old Estêvão made his first start in the Premier League after arriving from Palmeiras in the summer. And he impressed, providing an assist for Enzo Fernández's goal to make it 3-0 before halftime.
Chelsea had five different scorers, with João Pedro, Pedro Neto, Moisés Caicedo and Trevoh Chalobah also finding the net.
It was Chelsea's first win of the season after a goalless draw with Crystal Palace on the Premier League's opening weekend.