Sergio Perez has revealed pain in his left shoulder contributed to his poor qualifying result at the Spanish Grand Prix on Saturday.
The Red Bull driver will start Sunday's race from eighth on the grid after qualifying over 0.9s off teammate Max Verstappen, who will start second.
Perez spun at Turn 13 on his first attempt in the final session of qualifying before managing the eighth fastest time on his second attempt.
"I didn't felt 100% with myself today," he said. "I had a bit of an issue with my shoulder through qualifying and was feeling bad all the way through it.
"I've spoken to the team and we reviewed everything and we should be back to 100% tomorrow."
Perez was not sure how he had sustained the injury but said the pain got worse during the session.
Asked if it contributed to his disappointing performance, he added: "It was just a bad day.
"I didn't get a good lap throughout the day. Q1 was looking alright but we just didn't make any progress after that.
"But I wasn't 100% so it was hard to get the best out of the car in qualifying."
"[It was] the toughest qualifying, not feeling 100% physically was a big limitation."
Perez has already dropped 39 points to teammate Verstappen in the first three races of the 2021 season and admitted he is still not getting the maximum performance from the car.
"Yeah it's a matter of time," he added. Today it hasn't been a good weekend overall.
"From my side, I think in the past you see things are starting to come, especially the pace, long run pace, and some work to do on performance, that's it.
"Just getting to know the car a bit more will be key."