Chelsea crushed Arsenal 3-0 in a preseason game in Beijing on Saturday but the friendly turned ugly as Pedro left the field with a bloodied face after a big collision with David Ospina.
The injury scare was followed by a two-goal performance by Chelsea's Belgian forward Michy Batshuayi before a crowd of 55,618 people at the Bird's Nest in the Chinese capital.
Pedro lay on the ground within half an hour with blood in his nose, lips and right ear after colliding with Colombian keeper Ospina, who slammed into the Spaniard as he leapt to clear a long ball with both fists.
After a few minutes of medical attention on the ground, the Spanish international walked off the pitch and did not return to the game.
The victory gave the Blues some measure of revenge after Arsenal stunned Chelsea 2-1 in the FA Cup final in May to deny the Premier League champions a double trophy season.
Batshuayi shined as Chelsea prepare to be joined by Spanish striker Alvaro Morata, who could make his debut against Bayern Munich in Singapore on Tuesday following his reported 80-million-euro ($92.2 million) transfer from Real Madrid.
Batshuayi scored his second goal within five minutes of the second half, deftly one-timing a low pass from Marco Alonso from just outside the area to fire a curving shot past Ospina.
Arsenal's own star signing, former Lyon striker Alexandre Lacazette, had a low-key first half and did not return for the second period.
French international Olivier Giroud entered the game in the second half and provided some spark but his early shots were saved or wide.
Willian opened the score sheet from just inside the area in the 40th minute, taking a low shot with an Arsenal defender in front of him to beat a diving Ospina.
Just two minutes later, Premier League Player of the Year N'Golo Kante took the ball inside Arsenal's half and fed it to Batshuayi, who beat Ospina with a left-footed shot from the edge of the box.