Arsenal pulled off the seemingly impossible by defeating Bayern Munich 2-0. You read that right: Arsenal defeated Bayern Munich 2-0.

This was the fifth time in three years the teams had faced off in the competition, and Arsenal managed to win its first of three games at home. The team had lost 3-1 in 2012-13 at the Emirates and then lost 2-0 at home the following year; the team did manage a win and a draw in Munich in the return legs, but those were all but formalities for the German side.

So what exactly went right for the Gunners this time?

In a recent analysis, WhoScored noted that there is a correlation between shots on goal and standings in the Premier League. In the two previous meetings with Munich, Arsenal was outshot 17-10 in the first home match and 27-8. In this recent win the team was still outshot, but the stats were 21-13. But there was a big wrinkle.

In 2012-13, Munich had six shots on target to Arsenal's three. A year later the shots on target were 5-4. This year? Arsenal held a 8-6 edge in that department. Two of those eight shots wound up in goal.

In 2012-13, Arsenal only dispossessed Munich eight times while losing the ball 19 times. A year later it was a 5-4 margin in Arsenal's favor. Of course in the first meeting Arsenal controlled possession while the latter meeting saw the Gunners concede possession dramatically (75 percent in Munich's favor!). This year Munich still held a steep possession advantage but Arsenal stripped the ball from the opposition 19 times while only losing it 11. That is a big number in terms of disrupting flow and avoiding a team like Munich from getting set up.

Those statistics tell part of the story, but there was arguably one other major factor to consider.

Petr Cech might have been the biggest difference maker, avoiding the fate of Wojciech Szczesny in past home games against Munich. In the 2012-13 match the Polish keeper conceded a howler. In the second game he made a poor tackle that earned him a red card, killed Arsenal's momentum and left the team open for the beating. Cech showed no such lack of poise and made six saves on the night. While he was in no way as spectacular as his rival Manuel Neuer at the other end, he made no mistakes on the night, something that Neuer cannot claim.

That is why Arsenal paid so much to get him. That is why he should have been playing in the UCL from the get go.