Caleb Porter isn't known around MLS as a man who particularly enjoys losing, but it's a good bet that the Timbers' MLS Cup-winning manager has never greeted defeat with such open arms as he did tonight.

In the Simple Invitational and preseason finale at Providence Park on Saturday night, the Timbers lost 2-0 to the Chicago Fire. It marked the first time since last October that a lineup consisting of Portland's best available players has been beaten.

Porter's post-game message was that this isn't going to be easy. The ecstasy of the Timbers' 2015 run is still very much in the air in Portland — indeed, the championship banner will be raised before first kick next Sunday — but the hope is that any feelings of invincibility bouncing around the corridors of the old stadium have been expelled.

The Timbers are beatable. The odds are very much against them repeating as champions this year. This loss to the Fire — MLS' worst team last year — wasn't so much a wake-up call as it was a reminder: Nothing comes easy in this sport.

So long as Dairon Asprilla — who crumpled to the turf in the second half — is given the clean bill of health he's expected to receive, there won't be any lasting damage from this game. The holes the Timbers need to plug, and the work they need to do, is in the details.

The Fire, under the direction of new coach Veljko Paunovic, surprised the Timbers by rolling out a 5-3-2 — which transition to a 3-5-2 in attack. It was an effective deployment in that it stymied the Timbers where they are strongest: the middle of the field.

With the trio of Darlington Nagbe, Diego Valeri, and Diego Chara struggling to find space and feed Fanendo Adi, Portland instead had to look to wide for offense.

And wide is where this team is waffling.

Between Zarek Valentin and Lucas Melano, the Timbers left flank verged on useless. Melano's ability to turn games with his speed notwithstanding, he's going to continue to frustrate this year. Approaching his second season Stateside, the winger is still struggling with the fundamentals — and in a game that took a considerable amount of mental fortitude to crack, he quickly faded.

Portland's task in breaking down Chicago's defensive setup only got harder at the end of the first half, when the Timbers conceded twice. After giving up an early goal when Michael Harrington hit an unmarked Arturo Alvarez in the box, the Fire made it two when Gilberto finished off an Alvarez free kick.

While the Timbers were better in the second half, applying plenty of pressure, they never looked truly threatening. Asprilla's injury was the most important moment of the period, and even if he misses just a week, his absence will hurt.

That's because Asprilla — and Melano too, for that matter — has no true replacement. After striking out on signing a Liga MX player last week, the Timbers are about to enter the regular season with no backup wingers. In general, attacking depth is an emerging concern.

In short, the Timbers don't have enough pop off the bench. The fact that Porter only used two of his subs spoke volumes — at this point, only Ned Grabavoy and Jack McInerney are considered worth bringing into games in which the Timbers need to score.

That isn't going to cut it. Grabavoy is a nifty player, but he's hardly a game-changer. McInerney, meanwhile, had an abysmal week. If his passing doesn't improve, he's not going to be worth the goals he scores.

Considering how devoid the Timbers are of secondary attacking options, it's paramount that they get the first goal in games. This team figures to be much better playing with a lead than playing from behind — a fairly novel concept for this franchise.

Defensively, Portland missed Liam Ridgewell. After winning a number of plaudits for his composed preseason performances, Jermaine Taylor disappointed. Organizationally, Taylor and Nat Borchers were frequently found wanting.

Left back remained an issue as well. Coming into the game, Porter's plan had been to swap Valentin and Taylor at some point — giving the Jamaican the chance to audition for the job in the Chris Klute's stead.

But with the Timbers going down in the game, that switch never happened — but chances are that Valentin's uneven performance means that the position is still very much up for grabs going into Opening Day.

It wasn't that the Timbers were terrible. They won almost twenty corners, and took over twenty shots. But they lacked tenacity in all phases of play. After sailing through the majority of the last two months, this conclusion to preseason should keep Portland honest.

Chicago is going to be fascinating this year. They have a number of terrific young players, a very bright manager, and a lot of growing up to do. But with all due respect to the Fire, Columbus next Sunday is going to be tougher opposition.

When we last saw the Timbers in competitive action in Columbus last December, they were humming at a rate that is only possible in the very best of years after a very long season.

When the 2016 Timbers hit the pitch against the Crew, they won't be humming quite like they were. There have been loses and additions, and as it is with every MLS team in these early days, Portland has to figure itself out again.

There is nothing wrong with losing preseason games. And as last season showed us, there isn't anything wrong with losing regular season games in the spring and summer. But the Timbers need to get better. Saturday served as a reminder. In one week, Opening Day will serve as a welcome test.