It was a tough night in Porto for Arsenal as they were beaten by a last-minute strike from Galeno.
Riding on the wave of their recent league form, it seemed a perfect time for The Gunners to pick up their first ever win at Estadio Do Dragao.
However, it wasn't to be, as some chaotic in-game management in stoppage time cost them a valuable draw.
Arsenal twice had the opportunity to clear their lines deep into stoppage time. Declan Rice first lost possession uncharacteristically, but as Arsenal dealt with the first threat, the ball fell to Gabriel Martinelli who had the chance to consolidate possession and run the clock down.
Instead, he mishit a clearance and gave the ball straight back to Porto.
Even at this stage, Arsenal still had the chance to close the game out. As Galeno charged towards the box, Rice backed off and decided to engage far too late to pose a serious threat to the shot.
The Brazilian effectively had a free shot at goal and even then, questions can be asked about the starting position of David Raya.It was a super strike but one that was entirely avoidable at multiple phases of play.
Arsenal have shown themselves to be a side capable of producing big results domestically, yet there remains a naievity about them on the European stage.
Perhaps that is to be expected. This is the first time they've been in the competition since the 2016/17 season. Add to that the fact that they last won a Champions League knock-out tie 14 years ago and it makes for tough reading.
However, this is a side that needs to be viewed in their own right. They are a side lacking experience against Europe's elite, with many players making their debut in the competition this season.
They will grow; they will get better; there might just be some bumps along the way.In the group stage, Arsenal wilted under the intensity and pressure in Lens, but came back to hit their French counterparts for six in the reverse fixture.
They are a side that invariably rises to the challenges they are faced with.
Arsenal may be an inexperienced side, but they will need to learn the tricks of the trade on the job if they are to go deep into this competition.
Porto, led by the experienced Pepe, knew how to play the tie. They knew when to go down, how to disrupt the rhythm of the game, and when to take a tactical yellow.
They waited for their one opportunity and grabbed it with both hands.These lessons are brutal at this level.
There is no doubt that Arsenal are a superior team to Porto, but there is a time to push for a win and a time to take what you have.
As Arteta stated in his post-match press conference, "if you cannot win it, don't lose it."
If Arsenal are to turn this tie around, they'll need to learn from the mistakes they made in Portugal.
We know they are capable, but they now must prove they belong on the big stage.