The 21-year-old, who was signed out of the team's academy in prior to the season, scored Toronto's only goal Saturday in a 2-1 loss to the Seattle Sounders.
Osorio's effort seconds into the second half gave Toronto life but wasn't enough after Seattle (10-7-4) went up 2-0 in the first 45 minutes thanks to a Mauro Rosales strike and an own goal by Toronto defender Doneil Henry.
"It's a really big surprise but at the same time it's not because I knew if I worked hard good things would happen," said Osorio, who's also picked up his first four caps for the Canadian national team this year. "I have talent to play in this league so if I work hard I will improve the weaknesses that I have and make them better. I know I'll be a good player in this league."
Much of the talk prior to the game surrounded star American forward Clint Dempsey, who was making his debut for the Sounders. Dempsey came off the bench in the first half but failed to score.
Osorio was stirring the drink early for Toronto (4-11-8) and could have given the hosts the lead just two minutes into the game when he collected a pass from Matias Laba on the left side, cut towards the middle and unleashed a curling right-footed shot that just went wide.
Seattle's opening goal came in the 16th minute thanks to some slack Toronto marking.
Eddie Johnson ran onto a cross from the left side and headed the ball across goal where there were three green Seattle shirts waiting with no Toronto players in sight. Rosales had ample time to chase the ball, get his left foot on it and angle a shot past Joe Bendik.
"It was just two silly goals, two silly errors. I'm very disappointed in the first goal," said Toronto coach Ryan Nelsen. "The second goal was a bit unlucky and unfortunate but the lead-up wasn't good. Besides that, they played very well. I just think they didn't get that last pass right and it just didn't bounce their way."
Dempsey was called in with 11 minutes remaining in the first half after starting forward Obafemi Martins was taken off following a thunderous tackle by Henry.
Dempsey, a former Fulham and Tottenham player, got his first touch a few minutes later in front of the Toronto goal, but defender Ashtone Morgan took him off the ball.
Seattle doubled its advantage with five minutes remaining in the half when Lamar Neagle fed a cross in from the left side. Henry took a stab at the ball with his left foot but could only redirect the ball towards his own goal. With Bendik wrong-footed, the ball rolled slowly into the goal.
"It was pretty unlucky," said Henry. "Not much I thought I could do but I thought we played a really good game. It was really unlucky on my part but I'll just keep my head up and keep playing my game."
Toronto roared out of the gates to open the second half and Osorio got TFC back in it when he converted a quick passing play seconds after the opening in front of 18,776 at BMO Field.
The hosts pressed for a tie but were unable to get another goal.
"I'm really proud of the guys. I thought they played really well. They kept position really well. I thought they were creative going forward," said Nelsen. "They came out and they were determined and they showed the character and they showed belief and I'm just devastated for them that they didn't get what they deserved and that was something from that game."
Chasing the equalizer, Toronto continued to push and controlled much of the latter period of the game but the closest they would come was in the 60th minute when substitute Robert Earnshaw had a left-footed shot from just outside the penalty area come back off the post.
Toronto's Jeremy Brockie was played in alone in the dying seconds but he had his back to the goal and couldn't turn to convert the opportunity.
It was likely Brockie's last game in Toronto as his loan deal from the Wellington Phoenix of the Australian A-League is about to end.