With his eye on salvaging United's season in MLS, he rested his key players and started eight reserves.
The gamble failed, and United lost 1-0 before 7,214.
The result left United with little chance of advancing in the Champions League. The club sits at the bottom of Group A with zero points. After three consecutive losses, the team's only hope of advancing would be to win its last three games and get help from elsewhere. Two of those games are in Central America, where no club from United States ever has won.
“If we win this game we are still in it. Now it's going to very difficult,” Soehn said. “We have to focus on Saturday [against Chivas USA] now.”
The loss extended United's winless streak to seven matches in all competitions (0-6-1).
Cruz Azul also was guilty of fielding a weak team, with only three players starting from its 2-0 loss to Club America on Sunday.
With United's MLS postseason bid in jeopardy, Soehn used the game as a workout for his second-tier players and starting defender Greg Janicki, who made his debut with the club. The rookies held their own but in the end grew tired and were finally outplayed. United faces a crucial league game against Chivas USA at RFK on Saturday.
Francis Doe played as the lone striker in United's formation, with veteran Jaime Moreno playing behind him. Devon McTavish, playing as a holding midfielder, and defender Marc Burch were the only other regulars in the lineup.
Soehn had nothing to lose in starting Moreno. The striker was suspended for the club's next two MLS games and fined $500 after throwing an elbow against Andre Rocha in Sunday's 3-0 defeat at FC Dallas.
Moreno had an early chance, but his shot went too high.
Quavas Kirk, playing on the right flank, had a fine shot saved in the 23rd minute. Doe had the ball in the net moments later after finishing a cross from Moreno, but he was called offside.
Still, the effort seemed to promise better things, and the match was scoreless at halftime. United forward Ryan Cordeiro replaced midfielder Joe Vide, who was on a yellow card, after the break.
“The effort and the energy a lot of the young guys brought on the field, obviously mixed with the veterans, produced a good quality performance,” Soehn said. “Unfortunately the goal happened.”
Cruz Azul took the lead on a fluky goal when a shot from Gerardo Lugo was deflected in off Pablo Zeballos' back in the 56th minute. United goalie Zach Wells had no chance to stop the shot, which was credited to Zeballos.
Thabiso Kumalo, a second-half substitute for United, later hit the post. The result could have been worse as United held off a number of late attacks from the Mexican club, much to the cheers of the blue-shirted fans of Cruz Azul, who outnumbered United's supporters.
“The positive side is we worked really hard and put in a lot of energy. Unfortunately we come up with a bad result,” Moreno said. “The luck is not going our way, and it's something we have to fight against.”
United is 5-3-4 at home against Mexican teams; however, on the road the club is 0-7-0.
The Champions League features the best 24 teams from North America, Central America and the Caribbean. The winner qualifies for next year's FIFA Club World Cup. The top teams in the group advance to next year's knockout stages with the final played in April.