Victor Guzman headed the only goal as Pachuca advanced to the semi-final of the Club World Cup following an extra-time win over 10-man Wydad Casablanca.
The Mexican side will face Gremio of Brazil in Al Ain on Tuesday, after their hard-fought win over the champions of Africa in the capital.
Defeat was not popular with a crowd that was overwhelmingly in favour of the Moroccan club.
Wydad's manager, Hussein Amotta, had said before the game he was hopeful his side would benefit from some additional Arab support in Abu Dhabi.
Whether their number was bloated by new, locally-based fans for one tournament only or not, their backing was raucous.
Based mainly at the northern end of Zayed Sports City stadium, the red mass were rarely silenced, even though the game itself was shy on incidents.
The first half was memorable for little other than the excellence of the Wydad support, as well as the first yellow card via a video review in this tournament.
Ibrahim Comara was the recipient. After reviewing evidence on a monitor near the halfway line in the 39th minute, referee Ravshn Irmatov deemed a tackle by Wydad’s Ivorian centre-back on Angel Sagal to have been reckless.
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Attacking the goal behind which their supporters were banked, Wydad started the second half far more brightly. Ismail Al Haddad clipped the top of the Pachuca crossbar bar after a raid down the left flank.
Their impetus was halted unceremoniously, though, when Brahim Nakach, their robust midfielder and captain, was sent off after 69 minutes.
Having lost control of the ball on the edge of his own penalty box, Nakach lunged into a tackle on Jorge Hernandez, the Pachuca midfielder.
He went over the ball, caught Hernandez’s ankle, and was shown a second yellow card. It was reckless, and might have been worthy of a straight red card anyway.
The 10 men still carried a threat going forward, but were increasingly open at the back. As the 90 minutes edged towards a close, it was the Mexican side who looked most likely to break the deadlock.
In the second minute of injury time, Franco Jara had the clearest chance of the game, from a right-wing cross by Keisuke Honda.
Wydad were spared, though, as Jara could only direct his back-post header into the side-netting.
Despite being a man down, the Moroccan side rarely looked flustered in extra time, and forged chances of their own. Most notably, Reda Hajhouj blazed a drive from the edge of the box just past the post of Oscar Perez in the Pachuca goal.
That arrived just moments before the winner was scored at the other end, though.
Guzman rose in the middle of the Wydad area to a head a cross by Jonathan Urretaviscaya past the helpless Zouhair Larroubi in the Wydad goal.