Montero struck for two goals in an eight-minute span during the first half to put the Sounders in front, with Morris adding the third just before the final whistle off Cristian Roldan's second assist of the evening.
Montero found the opener just after the half-hour mark when the Sounders were awarded a penalty kick by referee Bryan López after Roldan was brought down in the León penalty box. That allowed Montero to step to the spot, where he drilled the finish into the top corner.
Montero added a second just eight minutes later, running onto a cross from Roldan and redirecting it past León goalkeeper Rodolfo Cota, giving the Sounders a 2-0 lead they took into the halftime locker room.
Seattle continued to apply pressure in the second half, racking up a flurry of chances, but finding a third goal elusive until Morris' late finish. The US international forward cashed home a close-range tally off another feed from Roldan, giving the Sounders a 3-0 cushion ahead of Leg 2 at Estadio León on March 17.
- THE BIG PICTURE: Playing without Designated Players Raúl Ruidíaz and Nicolás Lodeiro, Seattle could hardly have asked for a better start to this quarterfinal series. If anything, the Rave Green might feel a little snakebit that they didn't tack on a couple more, as the chances were flowing throughout the second half. Anything can happen in Leg 2, but this result puts the Sounders within arm's reach of a CCL semifinal berth vs. NYCFC or Guatemala's Comunicaciones FC.
- MOMENT OF THE MATCH: Montero's second was a well-worked team goal, extending the Colombian's club record to 70 career goals across all competitions.
- MAN OF THE MATCH: Just as he was in Seattle's Round of 16 series against Honduras' FC Motagua, Cristian Roldan was massive for the hosts.
- SEA: Saturday, March 12 vs. LA Galaxy | 3:30 pm ET (MLS LIVE on ESPN+ in US, DAZN in Canada)
- LEO: Saturday, March 12 vs. Tigres UANL | 6 pm ET | Liga MX