Union, based on the balance of play, probably deserved at least a draw and indeed it took a bizarre effort from on the goal-line, squeezed home by Karim Bellarabi (0.1 xG), in injury time, to clinch victory.
In truth both of Union's goals were of the highest quality too, with Christian Gentner (0.06) and Marius Bulter (0.07) converted low-yield chances. But even still, Leverkusen defied them, with Kai Havertz's (0.07) lob in the first half another unlikely finish. But a warning to heed for the title contenders is clear - their current run against xG seems unsustainable.
There seems to be a crazy game like this on a weekly basis, and this time we head to the Premier League and Villa Park for some all-round madness.
Most xG models, for obvious reasons, don't include own goals in their totals, meaning Villa scored once against an xG of closer to double that; a series of blocked shots and poor finishes from inside the area, particularly in the first half, was their downfall.
Spurs, meanwhile, were hugely profligate despite scoring three goals. Indeed Son collected nearly 1.4 xG from the same incident, with Pepe Reina saving his penalty before the same player prodded home the rebound.
Dele Alli was also extremely guilty, squandering at least three excellent one-on-one opportunities carrying at least 0.35 xG apiece. In the end the teams reached the right result but both will be concerned at their wastefulness in front of goal as they chase different objectives at either end of the table.
This is one of the cases where match state plays a key role in understanding and rationalising the xG. Bayern simply battered Koln in the first half, and could have been four up at half-time had Serge Gnabry (0.70 xG) somehow contrived to hit the post from close range.
The same player put Bayern 4-0 up in the second half, and only then were Koln even remotely in the contest. The Munich giants have a big Champions League game in midweek and clearly begun to conserve energy, allowing Koln to create (and miss) a host of chances, with Anthony Modeste particularly guilty.
In this match state Koln scored one and should have had at least another. But the game was already totally and utterly over and Bayern would not have been so generous had the game still been in the balance. So yes, the xG is close - but the game just wasn't - at all.
What is xG check?
Each week FC will aggregate the Expected Goals (xG) ratings from three respected sources and provide an average for both the home and away team. From there we will assess which matches have ended in a different manner than the xG would suggest.
EXPECTED GOALS (xG) assesses the quality of a shot based on several variables such as assist type, shot angle and distance from goal, whether it was a headed shot and whether it was defined as a big chance. From there that shot is assigned an xG score and the cumulative total of these scores provides a team's xG for a match.Stats Definition
But sometimes, xG doesn't tell the whole picture, so we also analyse the highlights of these games to look at the chances created by teams in a little more detail.