"He has shown no improvement in the Indian team. A good coach needs to come up with good strategies against specific opponents, should have good management and communication skills as well as ability to read the game. He is no coach," Carvalho told PTI.
However, Carvalho's former India and Mumbai teammate Mervyn Fernandis has questioned frequent changes of coaches.
"I do not believe in talking about coaching. That's my personality. We have made so many changes, brought in foreign coaches after using Indians, but where have all these changes got us to? And before making any change we should see what are the other options," Fernandis said.
The Indian team, led by Sardar Singh, failed to achieve its primary aim to qualify for the showpiece event at the World League semi-final at Rotterdam last month.
Nobbs's could be in the line of fire if the Indian team fails to earn a direct entry into the world cup by winning the eight-nation Asia Cup, which is slated to be held from August 24 to September 1 at Ipoh, Malaysia.