With a 3-0 advantage over Liga MX's Club León before the second leg of their Concacaf Champions League quarterfinal series at Estadio León on Thursday evening (8:30 pm ET | FS1, TUDN), Seattle Sounders FC are on the precipice of punching a semifinal ticket.

But there's seldom a safe lead in this tournament, as evidenced by New York City FC's chaotic second leg on Tuesday as Guatemala's Comunicaciones mounted a furious comeback to turn a 5-2 aggregate deficit into a 5-5 draw. NYCFC still advanced on the away goals tiebreaker, but it was nonetheless a reminder of what can happen in the wild world of CCL.

It all leaves Sounders head coach Brian Schmetzer seeking the right balance down in Mexico.

"We’re not going to go down there just to defend for 90 minutes. That would be foolish of us. They’re too good of a team," Schmetzer told reporters at Starfire Sports Complex on Tuesday.

"[The players] need to be laser-focused in the first 15 minutes, not just to defend and try to take the crowd out of it and all those things that we’re going to do," he later added. "But it’s also when we have a chance to play, I want them to be brave. I want them to be able to play."

MLS is closer to a CCL win than ever before

Seattle earned their 3-0 advantage after a strong performance in Leg 1, boosted by Fredy Montero's brace and an additional late tally from Jordan Morris.

The Sounders were without star striker Raul Ruidiaz (hamstring) for the matchup, and while the Peruvian international traveled with the team to León, it remains to be seen if he's ready to feature. Seattle will be without one of their starting center backs in Yeimar Gomez Andrade (ankle sprain), while Uruguayan playmaker Nicolas Lodeiro (quad strain) has resumed training with the team and looked "very good" on Tuesday, according to Schmetzer.

Knowing an early goal might put the series out of reach for Club Leon, Sounders right back Alex Roldan said they'll need to pick their spots to chase a road goal.

"We’re going to go over there and try to win this game. It’s not like we’re going over there to try and keep a 3-0 game," Roldan said.

"We all know that going over there is going to be a battle. We’ve played in Mexico before and know how difficult it is – weather, environment, altitude, fans," the El Salvador international added. "There’s a lot of factors that get taken into consideration, but at the end of the day we got to stay within the game. We got to make sure we go the first 45 without getting a goal conceded and close out the second half. [Then] we’ll be onto the next round and moving forward."

With León bound to throw numbers forward, Seattle could capitalize on counter-attacking opportunities. If the Sounders score, their Liga MX hosts would need to score five given the away goals tiebreaker.

"One of the good things about this team and this group is that these past few games, we all, even the fans, realize how good of a transition team we are," Roldan said. "So I think it works in our favor being patient, working defensively together and then finding our opportunity to go forward and get a goal with Cristian [Roldan] and Jordan stretching them in behind.

"We’re definitely going to try and exploit that, but at the end of the day we’ve got to go out there and play a good game and hopefully make it difficult on them as well."

The series winner advances to face NYCFC in the CCL semifinals come early April.