Estevao Willian was involved in worrying scenes in Brazil on Wednesday night.
The Brazilian winger scored as Palmeiras beat Bolivar 3-2 in the Copa Libertadores.
However, Estevao had to be stretchered off just moments into the second half in a potential concern for Chelsea.
The 18-year-old will officially join the Blues in the summer after turning 18 this week.
Wednesday’s clash in Bolivia took place at the Estadio Hernando Siles in La Paz.
The venue is located at 3,637m above sea level and is one of the highest stadiums in the world.
Visiting players are forced to contend with the impact of high altitude, which can affect their breathing.
It is understood this caused Estevao to vomit on the pitch against Bolivar before he was stretchered off.
The teenager fell to the ground shortly after the start of the second half, which caused him to be taken off.
He was later seen taking medication on the bench later in the match.
It comes less than three months before his long-awaited move to Stamford Bridge.
The youngster has already scored 22 goals and provided 11 assists in 68 senior appearances for Palmeiras following his goal last night.
Speaking this week, he opened up on his upcoming move to Chelsea.
Estevao told The Players’ Tribune: “I think this transition to European football will help me grow even more as a player. Especially since [I’m] going to one of the biggest clubs in the world.
“A lot of people are asking me why we chose Chelsea, but they don’t understand how much Chelsea wanted me, and how much belief they have in my potential.
“Those people don’t know about the project they presented to us. To a young player, these things matter a lot, and I know we’ve made the right decision to go to London.
“Until then, I simply want to enjoy these last few months at Palmeiras. You know how hard it will be for me to leave the Palmeiras fans. The truth is that I barely even know what to tell them.
“From the first moment I stepped on the pitch, they have shown me so much love and affection.
“To know that I’ve been able to give them joy in return… It’s a priceless feeling. This club will always have a special place in my heart.”
Chelsea completed a deal to sign Estevao last summer but have had to wait for him to turn 18 to officially join the club later this year.
