After failing to win in Australia and Bahrain, reigning world champion Hamilton's season hit a low in China as both he and Mercedes struggled.
"Both on my side but also as a team, we've been underperforming," he said.
"From my side it was a disaster. I'll have to look at it so I can stop losing points and get back to my normal performance level."
Yet Hamilton's teammate Bottas managed to finish second in China, and he also almost won in Bahrain, so the Finn says that his world championship target remains on track.
"Yes, that's my goal and that's the way it should be," Bottas told AS.
Told that he has to keep beating Hamilton in order to achieve it, he admitted: "I believe in myself, so yes. That's the goal."
Amid Hamilton's current contract negotiations and his obvious dip in form, boss Toto Wolff urged the Briton to up his game.
"Like the car, he might not have been quite there this weekend," he said in China.
"I still think he's the best driver, it's just that even the best have days when they're not at 100%," Wolff added.
Hamilton's former teammate Nico Rosberg agrees, telling RTL: "Lewis is not in form but he's always had such phases.
"If he's not confident, he starts to think and he makes mistakes. I'm curious to see if he comes back in Baku."
Baku plays host to the fourth race of the season in two weeks' time.