Kolkata, Mohammedan Sporting suffered a heartbreaking defeat in their Indian Super League debut, conceding an injury-time goal to newly crowned Durand Cup champions NorthEast United FC here on Monday.

Replacing Nestor Albiach in the 57th minute, NorthEast United's Moroccan midfielder Alaeddine Ajaraie had a moment of brilliance in the fourth minute of injury time (90+4), calmly scoring the goal to give Mohammedan Sporting a tough reality check.

Despite showing resilience and flashes of promise throughout the match, the Andrey Chernyshov-coached Kolkata team, which gained promotion to the ISL after winning the I-League last season, squandered several opportunities.

"They are a much more experienced team and winning the Durand Cup gave them valuable game time ahead of the season," said Russian coach Chernyshov.

"We deserved at least a point in this game, but I am proud of the boys' performance. They showed great promise and I am confident that we will continue to improve with each game."

The match was also the first at the Kishore Bharati Krirangan in the Eastern Metropolitan Bypass, where some 4,000 passionate Mohammedan Sporting fans packed the stands, waving their black and white flags to celebrate their long-awaited debut.

The first half was characterized by a cautious encounter, with both teams testing the terrain without taking many risks.

NorthEast United's Jithin MS and Mohammedan's Alexis Gomez tried their luck from outside the box, but neither goalkeeper had any real problems.

Mohammedan SC, missing key players Abdul Kadiri Mohammed and Mohammed Jassim due to injuries, looked organized defensively but lacked cutting edge in attack.

In the early stages, Mohammedan looked dangerous, with winger Lalremsanga Fanai showing flashes of brilliance.

He won several fouls on the right flank, keeping the NorthEast United defense on its toes.

However, the Kolkata team struggled to create clear-cut chances in the final third, with most of their attempts coming from long range.

Alexis Gómez, his creative spark in midfield and number 10, came closest to scoring with a long-range shot in the 48th minute, but his shot went wide.

The Highlanders, on the other hand, got involved in the game as it progressed. Their playmaker Guillermo Fernández orchestrated their midfield and they looked particularly threatening on set pieces.

In the 60th minute, Ajaraie's shot from outside the box was blocked and, minutes later, Jithin's shot skimmed the crossbar.

Subran was lively throughout, continually testing Mohammedan's backline with his quick runs.

The match took a physical turn in the second half, with both teams receiving several yellow cards as tempers flared.

Mohammedan's Amarjit Singh and Mirjalol Kasimov, as well as NEUFC's Míchel Zabaco and Dinesh Singh, were booked in quick succession, as the match became a battle of attrition.

Both teams were forced to make substitutions due to injuries, which disrupted their rhythm.

Mohammedan suffered a heavy blow when his number 10 had to be substituted in the 91st minute due to an injury.

The decisive moment came after prolonged pressure from NEUFC.

In a quick attacking move, Thoi Singh received the ball on the right flank before sending a low cross into the box.

The Mohammedan defense failed to clear the ball and Ajaraie took advantage, controlling the ball with his first touch before calmly firing a left-footed shot past goalkeeper Padam Chettri from close range.

Chhetri, who had made a good save in the 58th minute, looked dejected when the goal surprised the Mohammedan fans, who expected his team to hold on for at least a point.