Pietersen referred to India's 2-0 Test series win against world champions Australia and said his team lost to a formidable side.
"India is playing fantastic cricket at the moment. It was a learning curve for the youngsters and also the guys who have been around. It's never nice to lose a series and we are now 4-0 down in the series. But it was against a side which has beaten the mighty Australia, and now England," Pietersen said.
Merciless India gives pink slip to Eng in IT city
Trailing the seven-match series 0-4 and facing a possible whitewash, Pietersen said England's attack had lost its firepower in India's placid tracks.
According to him, the Indians are generally vulnerable to swing and bounce but the tracks here were quite unresponsive.
"It has been a totally different ball game here," Pietersen rued.