The Toronto FC rebuilding process looked more like a demolition Saturday.

The Philadelphia Union was swinging the wrecking ball in a 6-2 dismantling of TFC in a Major League Soccer game at BMO Field.

Justin Mapp and Danny Mwanga scored two goals apiece and Gabriel Farfan and Kyle Nakazawa also scored for the Union, whose six goals marked a franchise-worst for Toronto.

Maicon Santos scored both goals for Toronto (2-5-6), who pulled to within 3-2 with an early second-half flurry before letting the game get away to the frustration of the 20,122 fans at BMO Field who booed Toronto off the pitch.

"That was a bad, bad performance by us," said Toronto head coach Aron Winter.

The Union had scored a total of eight goals in its 10 previous games this season.

"Of the six goals, at least five were given away," Winter said. "Today was not good. When you're rebuilding you have your ups and downs. After a defeat like today we need to stay calm. You have to still have faith."

But he also is putting some of that faith in the transfer market that opens in June. He said he will be looking for help.

"It's very frustrating," goalkeeper Stefan Frei said. "You feel very helpless. Everything we did today went wrong. Confidence-wise it doesn't help you as a goalkeeper to get scored on six times at home.

"The first touch for me was getting the ball out of the back of the net. That's something I'm going to reflect on and the team as well and we have to learn from it and bounce back next week."

Toronto defender Ty Harden said the ugly loss is something he and his teammates won't soon forget.

"If you're not motivated by that, if you don't want to prove that you're much better than that, there's something wrong with you," Harden said.

Philadelphia (6-3-2), in only its second season in MLS, thoroughly dominated fifth-year Toronto in the first half, scoring its first goal in just the second minute of action. Prowling the right side of the box, Farfan gathered in a cross from the left sideline by Jordan Harvey and put his right-footed shot into the bottom left corner past Frei.

Mapp made it 2-0 in the 11th minute on a left-footed shot from outside the box into the bottom right corner.

Not long after, fog started to settle in above BMO Field -- an apt description of the home team's state of mind. A prime example came when Joao Plata sent a pass just outside the Philadelphia penalty area that Santos missed entirely.

Toronto did show some life in the 35th minute when the elusive Plata set up Richard Eckersley who blasted his left-footed shot from just outside the area slightly high of the goal.

Hopes of a Toronto comeback suffered a blow just before the end of the first half on a splendid goal by Nakazawa, a right-footed shot from the centre of the box to the bottom left corner with assists by Mwanga and Sebastien Le Toux.

Santos injected some life into Toronto with a goal in the 50th minute, breaking in after taking a long pass from Eckersley. He worked around 'keeper Faryd Mondragon who had come well off his line and fired the ball into the middle of the empty net.

Santos scored again in the 60th minute from close in to pull Toronto to within a goal. But Philadelphia dashed any hopes of a home-team victory two minutes later when Mapp scored his second goal of the game on a left-footed shot from outside the box into the upper left corner.

"I think we had the game (at 3-2)," Harden said. "I think we had control of the game. We had them on their heels. We were incredibly stupid, naive to keep playing the way we played up to that point.

"If we had a little bit of composure going forward from that point on and kept maybe one person back, whatever, put in that extra effort, I think we had a chance to get the point if not win it."

Philadelphia, looking for its first road victory since March 19 at Houston, scored again in the 72nd minute when Mwanga converted a cross from Le Toux, then further embarrassed Toronto in the 89th minute with an easy goal by Mwanga.

Toronto made two changes to start the second half with Javier Martina and Danleigh Borman replacing Julian de Guzman and Dan Gargan. Winter said he hasn't been pleased with de Guzman's past couple of performances.

NOTES: TFC was without injured forward Alan Gordon (groin) and midfielder Jacob Peterson (hamstring). . . Toronto's next game is next against Sporting KC at BMO Field on June 4. . . Philadelphia and Toronto split their two games last season, each team winning at home. . . TFC was looking for its first win since May 7, a 2-0 decision over Houston. The other MLS win this season was against expansion Portland 2-0 on March 26.