The RSL midfielder had a chance to win the MLS Cup for Real Salt Lake, but his penalty kick was blocked by Sporting Kansas City goalkeeper Jimmy Nielsen, and Real went on to lose in the 10th frame.
Velasquez has lived with that memory for three months, but he hadn't watched the video of his missed shot until three days ago.
"I re-watched it, and it just broke my heart because I was so close," Velasquez said. "Also, I've always been that type of player that I want to live for moments like that. I was so excited to be the one to try and win it. All the guys were excited and they told me, 'You're going to win this for us, kid.'"
Ironically, Velasquez had just scored the biggest goal of his life in the Western Conference Semifinals against the Galaxy, so his confidence was sky high. But this moment humbled him forever.
"If you want to be a big player, you have to have a moment where you have a big fall," Velasquez said. "You just got to get right back up from it if you're going to be even bigger than what you expected. So, I think that was my moment. It definitely changed me and changed the way I look at the game."
Velasquez was devastated, but sought comfort in teammate Javier Morales, who had missed a crucial penalty kick when he was playing in Argentina.
"To see what Javier Morales is today and know that he had gone through moments like that, it kind of made me feel better," Velasquez said. "I think it's going to help me for the rest of my career."
Velasquez has battled a hamstring injury in preseason, but has been impressive enough to challenge for a starting position. At the very least, he will have an increased role with the team this season.
"Sebastian has had a great preseason," said head coach Jeff Cassar. "Expect a big year from him. He's starting to chomp at the bit for getting into that starting lineup. I think he's adjusting well to knowing that there is going to be more asked of him."
"I'm always excited when they tell me that I need to step up," said Velasquez. "I know that opportunity will be there on the table for me, so I'm ready to make the best of it and hopefully I can have a great season."
As for the haunting memory from Kansas City, Velasquez says he will take that missed opportunity and turn it into an opportunity for redemption.
"It definitely made me open my eyes to see that if you want to be a big player, these are the moments that you have to take advantage of," he said. "Obviously in that situation, I didn't. But hopefully I can get that same moment that can happen this year again."
Velasquez and Real Salt Lake open the 2014 Saturday night against the L.A. Galaxy at 8:30 p.m. on ABC 4.