For the first time this season, midfielders Roland Alberg, Tranquillo Barnetta, and Ilsinho started a game for the Union together, and they provided the desired offensive results.

With Alberg scoring the second hat trick in franchise history, the Union defeated the Chicago Fire, 4-3, Wednesday night before 16,667 at Talen Energy Stadium.

The Union (7-4-5, 26 points) retained their lead in the Eastern Conference, while the Fire (2-7-5, 11 points) remained in last place.

It was the most goals the Union have scored this season but also the second straight game in which they have allowed three after a 3-2 road loss Saturday to New York City FC.

Alberg, Barnetta, and Ilsinho are most dangerous in their ability to break down defenders, which all three did to create relentless pressure.

"The three of us know each other, play well together, and the coach knows the way we play, and hopefully we can play more games together," Alberg said.

Barnetta played as a holding midfielder, but he didn't abandon his attacking duties, either.

"It's nice to play with those guys," Barnetta said of Alberg and Ilsinho. "We have a pretty good understanding and like to play one-touch."

The Union faced a quick deficit when Chicago's David Accam turned on the jets, blew by the Union defense, and scored on a breakaway in the second minute.

Alberg had a hand and almost a foot in the first goal after he hit the post. The ball bounced out and deflected off Fire defender Jonathan Campbell for an own goal in the 11th minute.

In the 15th minute, Barnetta hit the post, and the ball rebounded off teammate Fabian Herbers right to Alberg, who scored from six yards out.

The Union went up, 3-1, during first-half stoppage time, when Barnetta fed Herbers, whose shot was blocked by keeper Sean Johnson. Alberg got the rebound, had his shot blocked by Johan Kappelhof, but then put in the ensuing rebound.

Alberg made it a hat trick when he scored on a penalty kick in the 56th minute after Chris Pontius was taken down in the box.

The only other hat trick in Union history came during their first season, on April 10, 2010, by Sebastien Le Toux against D.C. United.

Leading by 4-1, the Union allowed goals off corner kicks in the 69th minute to Razvan Cocis and in the 80th minute to Khaly Thiam.

"Second half as an attacking team [we get] A-plus, second half as defensive team: F," Union coach Jim Curtin said. ". . . On a different night, we could have been punished."

mnarducci@phillynews.com

@sjnard