Alvarez, also making his first MLS appearance, chipped beautifully to set up Daniel Steres' 68th-minute equalizer, then had the touch that paved the path to Zlatan Ibrahimovic's winner 12 minutes later.
He came on, in the 60th minute for rookie Emil Cuello, to a rousing fanfare from the sellout crowd at Dignity Health Sports Park, then provided a spark as the Galaxy, whose early control waned after Romain Alessandrini departed after 20 minutes with a hamstring injury, regained command down the stretch.
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“When you have the fans cheering to you, like they do in his case, you get extra motivated,” Ibrahimovic said in LA's locker room afterward. “But he's only 16 years old. Don't forget his age.”
The Swedish star on Thursday said of Alvarez, just a high school junior, that “one thing is for sure: There's not a 16-year-old close to him [talent-wise] in this league.”
If so, the Galaxy aren't ready to anoint him yet.
“It's very difficult to talk about him, because he's 16 years old ...,” Barros Schelotto said during his postgame news conference. “It depends about his future, about himself. If he works like a professional and is professional, then he will be the right professional.
“He can read tomorrow's newspaper or hear news about him, so he needs to keep working. We are working with him about that. He looks like 20, 22 or 23. He has a beautiful left foot. Even today, he made three or four passes, but he can be better, much better. ... The point is to keep him growing, not just that's it.”
Most 16-year-olds, Alvarez was told during his media session, are worrying about pimples, not on claiming three points for a pro soccer club.
“I'm actually worrying still about that,” he said, evoking laughter. “It's an honor, obviously, to step on the field at this age, but, honestly, I'm just trying to give my best for the club.”
The Galaxy were trailing when he entered, thanks to an ill-advised back pass from new center back Diego Polenta that CJ Sapong turned into a Fire goal four minutes into the second half. They pulled even after Alvarez's corner kick from the right wing was cleared back out to him, he cut past Aleksandar Katai toward the byline, then chipped with his left foot into the goalmouth. Steres nodded the cross into the ceiling of the net.
Alvarez in the 80th took a throw-in from Rolf Feltscher and with one deft touch put it on Chris Pontius's path. The shot rang off the crossbar, and Ibrahimovic's header on the rebound left Ousted sprawling into the net.
Ibrahimovic, who joked that he “knew Chris will hit the post and it will bounce straight to me, and I will head it,” has taken Alvarez under his wing.
“I slap him if he don't do what I tell him. That's what I do,” he said. “Nah, he's a good guy, he's a good kid. He works hard, he listens, and he wants to improve, he wants to get better. ... The coach has to take care of him the right way, so he needs to work hard, he needs to focus and not lose the focus because all the hype. Just continue to work.”