"You are always relieved after the first one, and I wanted to see how I fit in and wanted to get a comfort level," Pfeffer said. "I felt good, it was an enjoyable game, and my teammates helped me out a lot."
Pfeffer said he didn't know he'd be starting until he came to the stadium on Saturday evening.
"I think he was nervous as soon as he saw his name on the board, but during practice he was very good playing with the first team," team manager Peter Nowak said. "Everybody welcomed him warmly, and in the 60 minutes he played it was a good start."
Pfeffer was lifted in the 63d minute for Danny Mwanga.
The Union are 9-7-12 for 39 points, and moved within two points of Columbus, which began the evening leading the Eastern Conference.
Pfeffer, who signed with the Union shortly before his 16th birthday, has played in friendlies and reserve games, but this was his first MLS action.
It was another young player, 20-year-old Roger Torres, who continued his late-season ascent as one of the most productive on the team.
Torres set up the game's first goal. From near midfield on the right side, Torres sent a long cross on goal to Sebastien Le Toux, whose one-timer from just inside the box went past sidling keeper William Hesmer in the 32d minute.
"It was a perfect pass, and I was able to finish it with a good run," Le Toux said.
Le Toux, who began the season in a prolonged goal-scoring slump, now has seven goals and eight assists to lead the team in both categories.
Pfeffer had his best MLS scoring chance in the 42d minute on a play that was again started by Torres, who sent a long pass to Le Toux. Playing as a target forward, Le Toux broke down defender Eric Gehrig and found Pfeffer, who spun around and shot right at Hesmer from eight yards out.
Union keeper Zac MacMath earned his second straight shutout, but he wasn't seriously tested.
Contact staff writer Marc Narducci at 856-779-3225, firstname.lastname@example.org, or @sjnard on Twitter.