Did you notice? A handful of observations from Arsenal v FC Barcelona

FC Barcelona's well-earned 2–0 victory at Arsenal on Tuesday night in the first leg of their UEFA Champions League last 16 tie was everything a football match of this calibre should be — an absorbing, end-to-end battle replete with dangerous scoring chances that could have tipped the balance in either direction.

Here's a look at some of the little things that occurred during the game, a small selection of observations and ruminations that might have escaped the casual viewer. Which ones did you notice?

• Arsenal's Nacho Monreal was whistled for the first yellow card of the game after just six minutes of play for a middle-of-the-field foul on Ivan Rakitic. It was a clear message from the highly experienced and respected Turkish referee Cüneyt Çakır to both teams that rough and tough play would not be tolerated.

• Incredibly, the warning worked, as another yellow card was not issued until Barça's Gerard Piqué was slapped with a caution in the 85th minute, a foul that will cost him the return leg at Camp Nou.

• Almost inconceivably, though, in the 83rd minute, even when Lionel Messi was fouled by Mathieu Flamini in the Arsenal penalty area and was awarded a penalty kick, no yellow card was shown.

• Barça, who have been known for some uncharacteristically cold starts several times this season, looked calm and collected right out of the gate through the first quarter hour, doubling up Arsenal in passes, 95-42, and monopolising possession to the tune of 70%-30%.

• By the time the clock read 68 minutes possession was unaltered at 70%-30% but Barça's passing advantage had ballooned to more than triple that of Arsenal, 505-165.

• Messi nutmegged Laurent Koscienly at the top of the area in the 35th minute, leaving the Frenchmen with no remedy but to foul, a play that led to Barça's first dangerous chance of the game — a free kick that Messi, who normally shoots high in similar situations, slammed low into the wall.

• Arsenal's famous fan chants came out of hibernation in the 57th minute, the only time they made any real noise. Chalk one up for Barça, which did a great job of minimising Arsenal's home field advantage.

• In the 62nd minute, amidst an extended Barça possession that yielded back to back corner kicks, Arsenal were taking no chances and parked all 11 men back in their own penalty area.

• After Messi put Barça up 1-0 in the 71st, Mesut Ozil and the rest of his Arsenal teammates were standing agape near midfield, hands on hips, searching for answers. Arsenal had been creating sustained pressure at the other end and Barça's coast-to-coast counter attack goal was the very definition of a demoralising blow.