"This is a Montreal team that can cause a lot of problems," Curtin said.
He has a point.
A playoff team last year, Montreal is just 3-13-5 and has lost six consecutive MLS games. The Impact, however, did win, 1-0, Tuesday against El Salvador's C.D. Fas in the opening game of the CONCACAF Champions League.
If the Union feel any reason to be puffing out their chests, all they have to do is look at this year's results against Montreal.
The Impact are 1-0-1 against the Union. On March 29 the teams played to a 1-1 draw at PPL Park and then Montreal won at home, 1-0, on April 26.
In the draw, Union-killer Marco Di Vaio scored the equalizer in the 80th minute on an assist from former Union midfielder Justin Mapp.
A 20-goal scorer last year, Di Vaio, who began the season with a three-game suspension from a red card he received during a melee in last year's playoffs, has four goals in 15 games.
"We have a tough time dealing with Di Vaio for 90 minutes," Curtin said.
Di Vaio, who scored the goal in Tuesday's win, can carry a team, even one that has played as poorly as Montreal.
"You see him getting back healthy-wise," Curtin said. "He is a handful, a world-class goal-scorer."
Last Oct. 19, Di Vaio scored in Montreal's 2-1 win over the visiting Union. It was a crippling loss for the Union, and they did not qualify for the postseason.
During a 5-3 win over the Union last year in Montreal, Di Vaio scored three times.
Former Union forward Jack McInerney leads Montreal with six goals. He also scored a goal for the Union before his April 4 trade for Andrew Wenger.
Despite the presence of Di Vaio, Montreal has scored just 21 goals, tied for the fewest in MLS with Chivas USA.
The Impact have also allowed 39 goals, the second highest total in the league, behind Houston (40).
So the Union are clearly the favorite. Whether two-time Algerian World Cup goalie Rais Mbohli makes his debut for the Union remains to be seen.
Signed July 30, Mbohli will be the starter once he tells Curtin he is in game shape. Zac MacMath started the previous 56 games.
No matter who is in goal, there is no doubt that Di Vaio will get his attention.
Montreal Impact at Union
What: Major League Soccer, Montreal Impact (3-13-5, 14 points) at Union (5-8-9, 24 points)
When/Where: 7 p.m. Saturday, PPL Park.
Television: Comcast SportsNet.
Union at home: 2-2-5.
Montreal on the road: 0-7-3.
Goals for: Montreal 21, Union 34.
Goals against: Montreal 39, Union 36.
Last MLS game: Montreal lost at home last Saturday to Toronto, 2-0. The Union tied at Sporting Kansas City on Aug. 1.
Outlook: The Union are 2-1-3 in MLS games under interim coach Jim Curtin. . . . Brian Brown, in only his second MLS game, scored the Union's goal against Sporting Kansas City. . . . Midfielder Cristian Maidana, who missed the last two games with a hamstring injury, returned to training this week. Entering the weekend Maidana was tied for second in MLS with eight assists. . . . Sebastien Le Toux leads the Union with eight goals. . . . Impact defender Adrian Lopez is out with an ACL tear. . . . Former Union midfielder Justin Mapp has a team-high eight assists for Montreal. - Marc Narducci