Red cards, particularly in big games, between two of the best footballing sides in Europe, should be avoided as much as possible.
However, the referee can only go by the letter of the law, and that determination from Nicola Rizzoli led to Arsenal goalkeeper Wojciech Szczesny shown a straight red card a little past the half hour mark, and with it allowing Bayern Munich to completely and utterly dominate the home side in their Champions last 16 first leg tie at the Emirates.
For 35 minutes Arsenal more than held their own, scaring the Bayern defence no-end, and doing everything but score, with Mesut Ozil missing a penalty.
The next 55 minutes, however, after Szczesny was given his marching orders for a foul on Arjen Robben, was simple - Bayer possession, wave after wave of attacks, and determined, dogged Arsenal defending.
There was to be another missed penalty, this time from David Alaba, but also an absolute peach of a goal from Toni I-love-to-score-against-Arsenal Kroos, and the late dagger into Arsenal's heart from Thomas Muller, as Bayern took a near-impregnable 2-0 lead into the second leg at the Allianz Arena, in a match that was almost a carbon copy of Manchester City's 2-0 defeat to Barcelona on Tuesday night.
The eyebrow-raising news before kick-off was the inclusion of Yaya Sanogo in the starting lineup at the expense of Olivier Giroud. Maybe Wenger thought Giroud was not focussed enough for this game, or maybe the Arsenal manager believed Sanogo, who only made his first start for the club in the 2-1 FA Cup win over Liverpool on Sunday, would play without fear against the fearsome Bayern.
Whatever the reasons for the decision might have been, it seemed like a masterstroke from Wenger, with Sanogo making a bright start to the game, as Arsenal rampaged forward from the off.
However, it was Bayern who nearly took the lead, with Toni Kroos, who scored against Arsenal in the first leg at the Emirates last season, firing a brilliant long-range effort, which was equally brilliantly kept out by Szczesny.
It was all Arsenal for the next ten minutes or so, with Sanogo and Cazorla forcing good saves from Manuel Neuer, before seven minutes into the game, the home side were given the opportunity of their lifetime to take the lead against can-somebody-even-come-close-to-beating-us Bayern.
Jack Wilshere threaded through a pinpoint ball for Ozil, who broke free, before cutting back in from the left channel. In that process, Jerome Boateng hung out a left leg, which caught the Arsenal playmaker with the referee having no hesitation in pointing to the spot.
Ozil stepped up to take the penalty against one of his best friends in Neuer, and a stutter step later, the big right hand of the Bayern goalkeeper saw the ball kept from nestling into the net.
That missed penalty was like a big iceberg putting out the searing Arsenal fire, with Bayern, in typical Pep Guardiola fashion, starting to boss possession.
Arsenal, though, nearly broke through courtesy a brilliant pass from Sanogo and the pace of Alex Oxlade-Chamberlain, who again put in a great shift for the home side, and had it not been for the red card might have had more of a say in the attacking third.
Sanogo clipped a nice ball over the Bayern defence for Oxlade-Chamberlain to run onto. Bayern left-back David Alaba seemed to have the measure of the Arsenal midfielder, but such is the pace of Oxlade-Chamberlain, that even Alaba, a speedy gazelle himself, pushed the panic button, with Neuer coming out and just about sweeping the ball clear in the nick of time.
Arsenal lost their left-back Kieran Gibbs midway through the first half, with Nacho Monreal coming in his place, and Bayern started to dominate, with the majority of their attacks coming down the left.
Time and again, Bayern exploited space down the Arsenal right, with Santi Cazorla and Mesut Ozil struggling to do their defensive work, but the home side were comfortable enough, despite the German side's superior possession.
However, all it takes is a moment of brilliance or madness, and it proved to be a bit of both that led to Arsenal going down to ten men.
Toni how-good-is-this-guy Kroos clipped a ball over the top for Robben, who was allowed to run in behind by Monreal, with the Dutchman then nipping in ahead of Szczesny, who recklessly brought down the Bayern winger.
The red card came out -- the 100th under Wenger's reign -- but the opening goal still did not, with Alaba sending Lukasz Fabianski, in for Cazorla, the wrong way, but also firing his penalty onto the outside of the post.
Arsenal held on until halftime, but with a player less against easily the best club side in the world at the moment, it was just a matter of time before Bayern found the opening goal.
It came via the right boot of Kroos, who curled in an absolute belter into the top corner in the 54th minute for Bayern's 100th goal of the season.
Arsenal defended gallantly and it seemed like they might just keep it at 1-0, only for Philipp Lahm to clip in a ball three minutes from time right onto the head of substitute Thomas Muller, who made absolutely no mistake.
Kroos nearly got a brace, with a measured curler which just failed to creep into the bottom corner, instead hitting the post, as the defending champions planted a rather large foot into the quarterfinals of the Champions League.
At the San Siro, Atletico Madrid, courtesy a late Diego Costa header, won the first leg 1-0 against AC Milan.
