A possible strike three, to borrow a metaphor from another sport.
Then, in just a couple of weeks, it all turned around.
With three straight victories, Atlanta finally resembles the team that captured the MLS Cup title in just its second season and quickly became the league's flagship franchise.
The latest triumph came Wednesday night, a 2-0 victory over Toronto FC in a showdown between the last two MLS champions.
"You saw the confidence growing," de Boer said. "This is what you want, of course. We can improve and we have to improve, but this is a big step forward against a very good team."
It wasn't even close. United held a dominating 19-8 edge in shots, banging two off the post in addition to having two other apparent goals nullified by offside calls. Toronto didn't manage a single shot on net, making it rather easy for Atlanta goalkeeper Brad Guzan to post his third consecutive shutout.
The winning streak has certainly relieved the heat on de Boer, whose last two coaching jobs were measured in months rather than years.
After a successful tenure at Dutch titan Ajax, where he won four straight league titles, de Boer landed at Inter Milan in Italy's Serie A — only to be sacked less than three months into his tenure.
He moved on to Crystal Palace in England's Premier League, where a stunningly similar fate awaited. De Boer was fired after his team became the first in 93 years to lose its first four matches in the top flight without scoring a goal.
De Boer, whose long playing career is best remembered for a towering, 60-yard pass that set up Dennis Bergkamp's winning goal against Argentina in the closing minutes of a 1998 World Cup quarterfinal, came to Atlanta looking for redemption as a coach. But he had some huge shoes to fill, taking over for the wildly popular Tata Martino, who built the expansion club into a powerhouse before taking a job as Mexico's national coach.
Martino favored a freewheeling style that turned United into a feared offensive team, epitomized by Josef Martinez scoring a league-record 31 goals a year ago. De Boer prefers a more defensive-minded approach and switched to his favored 3-4-3 alignment, which clearly didn't mesh with the players he had in Atlanta.
When United was eliminated from the CONCACAF Champions League in the quarterfinals by Monterrey, United fans grumbled. When the team managed only one victory in its first six league games and was languishing in last place, the criticism of de Boer grew even louder — no small consideration given the team has set numerous attendance records during its brief history.
"The stature of the club is that they always want to be involved in the battle for the championship," de Boer said. "When the results are not good, there's always pressure."
But, to de Boer's credit, he kept tweaking the system, held a meeting to let his players air their grievances, and urged everyone to be patient during a time of transition.
"It takes time," the coach said. "You can't suddenly change suddenly from zero to 10. No, you have to go step by step. They had a great season last season. But it's a different season now."
If nothing else, the mood in the locker room has certainly improved.
"We feel good, we feel confident," captain Michael Parkhurst said. "We're growing game by game. We know that we're playing better soccer right now. We're getting the reward. We're getting goals and we're getting wins."
United is in the midst of a grueling stretch — eight games in 28 days — that leads into a 3½-week break coinciding with the Gold Cup.
By the time Atlanta begins its down time, the regular season will be nearly half over. By then, it will be much more apparent if the team has truly turned a corner and re-established itself as one of the leading title contenders.
"We're still missing a lot," Hector Villalba, who scored the first goal against Toronto, said through a translator. "But you can see that the team is getting results. We're starting to understand the ideas of the coach and to play like he wants us to play."