The left-back player sustained the injury in the second session of the match last night and was replaced by Mahesh Gawli in the 57th minute.
"X-ray examination showed his left toe has been fractured and his left foot is now on heavy bandage. He won't able to take field for at least four weeks," a team source said.
The injury will also mean that Mohun Bagan will miss Manju's services for the August 28-September 10 IFA Shield in Kolkata.
Manju's injury is also bad news for India, which is coping with the disappointing loss against Lebanon.
The other left-back, Sameer Naik, had a hamstring problem just a few days ago and Gawli, who normally plays in central defence, replaced Manju yesterday.
Meanwhile, the Ambedkar Stadium groundsmen have not got any specific request from the All India Football Federation to cut the grass on the pitch, which had made Houghton livid yesterday.
Houghton had said that the heavy grass on the pitch had given the taller and stronger Lebanese advantage as his boys could not play their usual ground passes.
Apparently, the groundsmen from the horticulture department of the Delhi government thought the barren patches of the pitch would be exposed if the grass was made shorter.
The groundsmen will do only the normal cutting done everyday but not to heavy level as they have not got any directive to do so, sources said.
The Indian players were also livid that the grass was so heavy for an important match of the home team in a tournament which is very important for the profile of the game in the country.
"We are the home team and it was an important match. But the opponents were given the advantage due to the heavy grass on the pitch. It is unimaginable that we were at the receiving end in a tournament at our home," a player said.
Another player felt bad for Houghton as the Englishman would be the one who would get the flak if the Indian team fails to enter the final, which is now a possibility, after an expensive six-week tour to Dubai and Barcelona.
"I felt bad for Houghton. We are also being criticised but it is Houghton who is feeling the heat in the media. He has invested so much in the team's good showing in this tournament and the future of the national team," another player said.
