The Brazilian winger showed why The Boss bought him in the summer, capping off a strong performance at Bunyodkor Stadium with a first-half strike. That proved to be the only goal of the two-legged tie as the Garden City club entered the last-four stage for the second time in three seasons.
After being held at home three weeks ago by the Uzbekistani outfit, Zlatko Dalic’s troops knew the stern task ahead. The Uzbek League leaders were unbeaten in their last 27 home matches, winning all their five previous games.
But the 2003 Champions League winners started brightly with Danilo Asprilla enjoying much possession but with no real end product.
In a scrappy opening 15 minutes, Lokomotiv gradually found their rhythm. It was not until the 22nd minute that Khaled Essa was called into action, denying Timur Kapadze’s low effort.
The hosts, playing in a half-packed stadium, pushed forward with Essa again needing to stop Temurkhuja Abdukholikov’s lame shot.
Al Ain’s real first chance came just after the half-hour mark. Asprilla turned away from his marker and his diagonal pass-shot had too much weight for Douglas to tap in.
But the home fans were silenced as Dalic’s men got their reward in the 39th minute.
Caio went on a bombing run and superbly set up Douglas, whose shot was blocked by Kakhi Makharadze. The ball then went back into Caio’s path, with the €3 million (Dh12.4m) purchase from Japan’s Kashima Antlers slotting home for the all-important away goal.
Despite needing at least two to progress, Lokomotiv began the second half cautiously. But it was the visitors who should have been celebrating.
Caio, dangerous on the left flank, found Asprilla with plenty of space but the Colombian winger smashed his shot straight at goalkeeper Ignatiy Nesterov.
That was the wake-up call Lokomotiv needed and they nearly got their equaliser when defender Nemanja Janicic hit the crossbar from a corner on 63 minutes.
Substitute Ikromjon Alibaev tried his luck from long range but his effort was punched away by Essa.
Both coaches brought in new faces but Asprilla continued to be a threat before being replaced by Mohamed Abdulrahman.