The 19-year old partnered skipper Robbie Keane up front and contributed a goal as the Galaxy moved through to the CONCACAF Champions League quarter-finals with a 4-1 aggregate triumph.
Villarreal was delighted to give so much to the Galaxy line-up as they get set to take on Mexico's Monterrey in the final eight.
"I was just happy to get that goal. It was my first shot of the game. I'm just happy that we got the result and we got that victory as a team," Villarreal told reporters.
"I was missing the guys a lot (while away with the US U20s). I'm happy to be back and now I'm excited for the Chivas game (this weekend).
"I was running up and down the field and I was hoping to get one chance and I'm glad that I put it in.
"It'll be a great match-up against Monterrey, they're a top team in Mexico and it'll be a good match up to see where we are. But I'm focused on the Chivas game right now and I'm just thinking about that."
Villarreal scored the Galaxy's second goal at The Home Depot Center in the 69th minute with a lovely run and finis with his left foot. That came after Omar Gonzalez gave LA an 18th-minute lead and before Keane and Jack McBean finished Herediano off who were served by an 85th-minute goal from Elias Aguilar.