Japan's Yuki Tsunoda apologised to AlphaTauri at the Spanish Grand Prix on Saturday for suggesting his car was "too different" from that of teammate Pierre Gasly.
Tsunoda, in his first season in Formula One, was only 16th in qualifying for Sunday's race while Gasly was 12th.
It was the fourth successive Saturday that the Japanese rookie had been out-paced by the more experienced Frenchman.
"It's always different feedback compared to my team-mate, it's the opposite," Tsunoda told Sky Sports.
"I have a little bit of a question mark if it's the same car... of course it's the same car but the character of the car is too different. I don't know why I was struggling this much."
However, later Saturday, the 20-year-old, who is 13th in the world championship to Gasly's 10th place, rowed back on his remarks.
"I wanted to apologize for my comments today," he wrote on Twitter.
"I didn't mean to criticize the team who have done a great job all weekend. I was just frustrated with my performance."