Lerg scored the game winner as the San Jose Sharks defeated the Edmonton Oilers 3-1 in a game between two teams out of the playoff picture.
The 29-year-old could barely believe his good fortune, scoring with 2:52 remaining in the third period after playing 353 minor league games while waiting for his NHL shot.
"I have no words, honestly," he said. "I put it in and kind of blacked out from there. It felt good to score that one, let alone to play this game in general. It has been a long seven years waiting for this. To finish like that, it is pretty exciting."
Sharks forward Logan Couture set up Lerg on the play.
"It's been a tough year, but things like that make it fun," said Couture. "He's waited a long time for this day. It was awesome. It was the most excited I have been about a goal since probably an overtime playoff goal."
Sharks head coach Todd McLellan said that Lerg's story is a notable one.
"It is a lesson for a lot of us, not only in hockey, but in life," said McLellan. "To persevere and follow your dreams and you will get there eventually and he got there tonight."
Patrick Marleau and Matt Nieto also scored for the Sharks (40-32-9), who snapped a two-game losing skid.
Nail Yakupov responded for the Oilers (24-44-13), who have lost four of their last five.
Lerg wasn't the only player to make an impact in his NHL debut as Edmonton goaltender Laurent Brossoit made 49 saves and nearly stole the game.
"It's obviously not the way I wanted to end the game considering how it was going for me," said the 22-year-old netminder. "But I have to take out the positives. I wanted to show well and show what I could do and I think I did that."
San Jose will miss the playoffs after qualifying for post-season play the last 12 seasons. The Oilers are on the outside looking in for the ninth straight year.
Edmonton dodged a bullet early on, killing off a boarding major assessed to rookie Curtis Hamilton just two minutes into the contest.
Brossoit was tested early and was forced to make 19 saves in the opening period.
Edmonton broke the deadlock with eight-and-a-half minutes to play in the second period as Sharks defenceman Justin Braun coughed up the puck in the slot right onto Yakupov's stick, and he beat San Jose goalie Antti Niemi glove-side for his 13th of the season.
Brossoit continued to stand on his head in the second, making a flurry of saves in the final minute with Tomas Hertl clanging a shot off the post.
The Sharks tied the game midway through the third on their 42nd shot after Justin Schultz gave the puck away to Marleau, who waited for Brossoit to go down before lifting it over him.
San Jose went up 2-1 with just under three minutes left as Couture sent the puck through traffic to Lerg at the side of the net.
Nieto added an empty-netter to give the Sharks some insurance.
Both teams complete their seasons on the road on Saturday as the Oilers are in Vancouver and the Sharks travel to Los Angeles to face the Kings.
Notes: In addition to Brossoit making his NHL debut for Edmonton, Hamilton was also playing his first NHL game… The Oilers have had 11 players make their NHL debuts this season.Suggest a correction