Atlanta United won its final home game of a happy regular season Sunday. All that money spent on the next-century retractable roof at Mercedes-Benz seemed almost worth it this fine day, with victory wearing a cap of bright blue and real, warm sunlight lighting up the faces of players celebrating at midfield. The home team even clinched a spot in this winter’s CONCACAF Champions League tournament, an achievement of hemispheric proportions.

A perfect day – almost.

Maybe two little events short of perfect, if we are to get picky. And with a postseason bearing down on the team with the best record in MLS, it is time to get picky.

If only United’s 2-1 victory over the surprisingly resistant Chicago Fire would have coincided with a loss by the Red Bulls, then all 71,000 or so at the Benz could have gone wild claiming the Supporters’ Shield. It was in the house, the shiny silver disc awarded to the regular season MLS champion. But it remained under wraps as the Red Bulls won their game and messed up the party. Now, United, with a one-point lead over the Red Bulls, must go to Toronto next Sunday and win this unique keepsake.

On one hand, it is a bit of a shame United couldn’t win the Shield here, because this is an award actually invented by the fans of MLS (funded by them, actually) as an appreciation for excellence of this long season. It is something by and for the fans, something that would have meant even more to a second-year team with an empty trophy case it is aching to fill.

“It would have been sweet (to win at home),” team captain Michael Parkhurst said. “Maybe it won’t be just as sweet, but it will be very, very sweet if we handle our business in Toronto and win it there. Of course, the perfect scenario you win it in front of your home fans. But if we can win our first trophy, period, next week, that will be amazing.”

“It would have been pretty cool to win it at home,” said Andrew Carleton, whose actual home (Powder Springs) is in the same metro area as United’s. He got a start Sunday with a couple stars – Miguel Almiron and Hector Villalba – on the shelf with injuries. “But it makes us want to win the MLS Cup at home even more. We’ll see how that goes.”

The kid served a good reminder, seeing how it’s the championship that anyone remembers, not the Shield. The Shield, if it comes, will be the first tangible achievement of this semi-new franchise, but still one that ranks below say a baseball league pennant in relative importance.

Toward that end, it is interesting to wonder just how much United’s Gerardo  Martino might want to risk in order to get Almiron and Villalba back onto the field in the pursuit of the Supporters’ Shield when there’s a bigger trophy to win. Both are nursing leg injuries. Almiron’s is a hamstring. Just the kind of problem that has a way of recurring if it isn’t given adequate rest.

And believe me, you want those guys when it’s time to play for a larger share of glory. You badly need those guys when it’s playoff time.

It’s not like just because United won Sunday, it didn’t miss those Almiron and Villalba (the team’s Nos. 2 and 3 goal scorers).

The winning goal Sunday was an own goal, deflecting off the foot of a sliding Chicagoan, Johan Kappelhof.

And United’s first goal was hardly suitable for framing. Josef Martinez was credited for an assist when he practically whiffed on a shot in front of the goal, catching just enough to deflect it in the direction of Franco Escobar. And he wrong-footed the ball into the net for his first-ever goal with United.

Take a picture because Escobar predicted you’ll never again see him score with his left foot.

Being just as critical as the point of the season demands, goalkeeper Brad Guzan will tell you that what United did Sunday was not good enough.

“You’ve got to be better in certain moments. We were carelessly giving the ball away. Bad passes. Bad touches. It wasn’t our sharpest performance,” Guzan said.

That leads to Sunday’s second shortcoming. With the absence of two offensive stars, with record-setting scorer Martinez a little out of sorts, going more than a month without a goal, this would have been the apt time for young Ezequiel Barco to step into the void.

Brought here with a MLS-record $15 million transfer fee, Barco, who’s a year younger than Ronald Acuna, was supposed to have a similar impact on this league as Acuna had with the Braves. Yet he has been tentative and quiet through most of the season, scoring four goals and contributing just three assists. He’s been injured. He’s been suspended. And, more to the point, he has been unimportant.

Sunday, Barco was in position to block a shot, which would have been a contribution if it hadn’t come off the foot of teammate Julian Gressel.

Earlier this week, Parkhurst said of the teenager, “Of course, we expect him to come in and do well. We see him in training and he looks hungry, he looks sharp, he looks quick – compared to the rest of us sometimes when we’re feeling a little heavy, he’s fresh.

“The important thing is that he doesn’t have that pressure that he has to do what Miguel does. He has to do what he does. What he does is good enough to pay a lot of money to get him.

“We expect – and I think he expects – to be able to come in and play well and connect with the team and connect with Josef up top and create things offensively. And I’m sure that he’ll do that.”

Still waiting.

But otherwise, don’t lose sight of the fact that Sunday was a pretty good day for soccer in Atlanta.