Chelsea boss Antonio Conte says Pedro came off at half-time against Arsenal due to an ankle injury, but hopes the issue will not prove serious.
Pedro, who missed a first-half opportunity in the 0-0 Premier League draw when he was denied one-on-one by Petr Cech, had earlier gone down for treatment after a challenge with Nacho Monreal.
Conte introduced midfielder Tiemoue Bakayoko in place of the former Barcelona forward at the break.
Pedro has now suffered three injuries in quick succession against Arsenal. First, he suffered a concussion and facial fractures after a pre-season collision with Gunners goalkeeper David Ospina in China.
The 30-year-old then missed the first league game of the season against Burnley due to another ankle injury he had suffered prior to being sent off in the Community Shield against Arsenal last month.
"After the first half Pedro was a bit injured because he had a kick on his ankle and then I change it, tried to have more balance in the midfield," Conte said after the match.
"Pedro took a knock to his ankle and wasn't 100 per cent fit. For this reason, I decided to make a substitution in the second half.
"We have to check with the doctor, but I hope this problem is not serious. We lost Pedro against Arsenal in China as well."
0 - Chelsea failed to score in a competitive home match under Antonio Conte for the first time (27 games). Stalemate. pic.twitter.com/fH8dDubjNK-- OptaJoe (@OptaJoe) September 17, 2017
The stalemate was the first time Chelsea have failed to score in 27 home matches under Conte, but the former Italy boss was not too disheartened, insisting people overlook Arsenal's quality.
Asked if he was surprised by Arsenal's display, he said: "No. Every game against Arsenal is always very tough, we knew very well what type of game we had to face.
"Both teams are great teams and I think it is a good draw. It was a good, open game with both teams trying to win. Both teams created chances to score.
"We started the game very well in the first 20 minutes and then we suffered a bit in the middle of the first half.
"But you forget Arsenal are one of the top six in England and, for this reason, we all know the type of game that we would face against them.
"Arsenal are a really good team, a strong team. They have a lot all over the field. But it's normal to find this type of situation when they are dangerous."