Substitute Enwer Annayev struck late as Turkmenistan's Ahal FK stunned Mohun Bagan Super Giant 1-0 in their opening Group C match of the AFC Champions League 2 at the Salt Lake Stadium here on Tuesday.
The all-important strike came in the 83rd minute when the 19-year-old forward, who had come on just minutes earlier, latched onto a precise through ball from Basim Gurbanberdiyew and slotted home his left-footed shot to the bottom right corner.
The two substitutes had combined almost instantly after being introduced in the 79th minute, with Gurbanberdiyew replacing Alibek Abdyrahmanow and Annayev coming in for Magtymberdi Berenow.
Gurbanberdiyew showed fine vision to thread the pass inside the box, while Annayev kept his composure to finish across the face of goal and secure a precious away win.
Earlier in the 32nd minute, Mohun Bagan had a close shave when Elman Tagayew's deflection off a low cross wrong-footed goalkeeper Vishal Kaith, only for the ball to come off the crossbar.
The ISL champions' best chance came in the 69th minute when Dimitri Petratos and Jason Cummings combined inside the box to set up Jamie Maclaren, but Ahal's young goalkeeper Kakageldi Berdiyev produced a brilliant save to deny the Australian striker from point-blank range.
Despite late urgency, Mohun Bagan struggled in attack, sorely missing the injured Manvir Singh.
Their wing play remained ineffective, while the defence looked rusty and error-prone, inviting pressure throughout the contest.
It was a nervy start for the home side as Ahal threatened as early as the second minute with Suleyman Mirzoyev charging into the box only to send his effort wide.
Magtymberdi Berenov and Mirzoyev continued to cause problems for the Mohun Bagan backline, which had to sit deep and absorb the early pressure.
Mohun Bagan finally got into the thick of things in the 13th minute with Liston Colaco and Sahal Abdul Samad both seeing their respective efforts blocked before surviving a close shave just after the hour mark when Tagayew was denied by the left post.
Mohun Bagan had a chance in the 37th minute, when Samad played a neat exchange with Jason Cummings, only for the Scotland native to fire his effort high from inside the area.
Ahal were left frustrated in the second half after Berenov's effort in the 52nd minute went to waste before seeing Mohun Bagan keeper Kaith thwart his effort five minutes later with a fine save.
Kaith came to Mohun Bagan's rescue again in the 69th minute when Jason Cummings charged into the box to set up Berenow at the near post but the Indian shot stopper used his large frame to close down the danger.
The game kicked up a notch at the 80th minute with Kaith pulling off another brilliant save to keep out Mirzoyev's follow-through header while at the other end, another chance went begging for Mohun Bagan with Abdul Samad pulling his effort just wide following a counter-attack.
The defeat leaves Mohun Bagan with some tough questions ahead of their next Group C outing, an away clash against Iranian giants Sepahan on October 21.
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