A missed penalty from midfielder Marcos Pereira in the first half proved expensive as Federation Cup champions Mohun Bagan went down 0-1 to Al Karama in the opening Group D encounter of the AFC Cup at the Khaled Ibn Al Waleed Stadium on Tuesday night.
Mohun Bagan were awarded a penalty when skipper Bhaichung Bhutia was brought down by Karama's Cameroonian defender Richard Bohomo inside the box.
However, Brazilian Pereira was unable to beat Al Karama goalkeeper Mosab Balhous from the spot in the 43rd minute despite being allowed to re-take the kick.
The let off proved costly as the hosts regrouped after the break with Mohamad Al Hamwi scoring the winner in the 60th minute.
He collected a rebound from Fahd Aodi and slotted the ball past Mohun Bagan goalkeeper Sangram Mukherjee.
The hosts got the first look on goal but Al Hamwi blew it over in the 17th minute.
But the green-and-maroons slowly got into the groove and Shylo Malsawmtluanga tested Karama goalkeeper Balhous with a shot from outside the box.
The custodian was once again brought into play when he denied Bhutia. Defensive midfielder Rakesh Masih then tried a long-ranger but was blocked by Balhous.
However, the missed penalty changed the complexion of the match and fortunes switched in Al Karama's favour.
The 2006 Asian Champions League runners-up could have doubled the lead in the 73rd minute but Al Hamwi's volley from a Hassan Abbas cross kissed the woodwork and went out.
Sangram had a good outing under the Mohun Bagan bar making some excellent blocks in the later stages of the match.
Mohun Bagan coach Karim Bencherifa was satisfied with his boys performance but refused to dwell on the missed penalty.
"We had a chance to take the lead from a spot-kick but this doesn't mean we could have secured the win. I'm satisfied with the performance," the Moroccan told the AFC website.
Al Karama coach Mohammed Kwid praised Sangram for his good work under the bar.
"Mohun Bagan had a golden chance to take the lead through the spot-kick and things would have been harder had they scored.
"We had a lot of chances to score in the second half but the Indian goalkeeper played well," said Kwid.
Mohun Bagan next take on Al Wehdat of Jordan in Kolkata on March 17.
The Jordanian club drew 1-1 with Kuwait SC in Tuesday's another Group D encounter.