San Diego FC made a fantastic start to their first Champions Cup campaign, dispatching Pumas UNAM 4-1.
Manu Duah, David Vazquez, Alex Mighten and Luca Bombino scored San Diego's goals in the space of 22 second-half minutes as the hosts roared back at Snapdragon Stadium.
Robert Morales' sensational bicycle kick put Liga MX side Pumas into a 1-0 lead in the 11th minute, but San Diego's pressure told after the break.
But San Diego talisman Anders Dreyer delivered for Duah to head home an equaliser in the 68th minute, paving the way for Michael Anthony Varas' side to surge to an emphatic comeback victory.
They will take a big lead into the second leg in Mexico City on February 10.
Peruvian team Forge drew 0-0 with Tigres UANL, while Ramon Juarez's late goal saw Club America beat Olimpia 2-1.
Data Debrief: San Diego get what they deserve
Pumas had just four attempts, and though they were clinical, with two of those on target, it would be fair to say San Diego were worthy winners.
They got off 22 shots (14 of which came in the second half), with seven of those on target – Pumas goalkeeper Keylor Navas had his work cut out.
In fact, five San Diego players managed to have three shots, as the hosts tallied up 3.18 expected goals to Pumas' 0.2 xG.
Dreyer did not get on the scoresheet, but he did lead the way for chances created (five), including his assist for San Diego's equaliser.