It's not about juicing numbers. It's about assigning a blanket value to a shooting event almost entirely based on from where the shooting event took place, and then deciding you can conclude how many goals you are expected to score based on that data. It's true that a 4th liner doesn't often get that many rebound chances but it does happen, and not all that rarely either. You can't dismiss these occurrences as not statistically significant and at the same time accept xG conclusions at their face value.
Expected goals, at least the publicly available models, don't sufficiently account for where the other players are on the ice. How one can possibly then call it a comprehensive appraisal of what has happened then?
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So even more than 10x what an Ovechkin one timer from his office at the top of the circle is worth in the model then. Totally flawless definitely.
Could really do without the condescension of "well you must not understand it if you think it's bad". I understand the model just fine and it's because I understand it I don't think it's worth as much as many of the advanced stat zealots do. The entire premise is flawed in its current form and paints a woefully incomplete picture of what occurred during a game.
You're telling me you are applying shooter-dependent and goalie-dependant modifiers for every expected goals-value you come across? Is that what you're doing? Come on. Frankly ridiculous is right. That's no longer a stat that is useful if you have to do a bunch of stuff to it after it's been recorded to make it meaningful. That's not rocket science, merely common sense.
Well if we're accepting a baseline blanket 'expected goals' stat applicable to all players and all situations it really shouldn't matter who is taking the shot should it? But it does. I never argued the the elite players aren't generating the most volume either.
Since you all took issue with my initial scenario lets explore a couple more for how xG is calculated. These are common occurrences in NHL games.
*I know different sites use differing models and apply different filters and gradients etc but they are all at their basic form built upon something similar to the posted diagram above.*
1a) Kevin Rooney starts his shift in the DZ. Loses the faceoff and spends the next 73 seconds along with his linemates chasing the puck around under pressure from his opponents. His goalie bails him out several times. Finally the opponent's fwd line tire and go for a line change leaving Rooney's defenseman in the corner with the puck for an easy breakout with lots of open ice. He passes to Rooney while the rest of his line changes. Rooney, being the responsible and boiler plate nothing NHL player he is knows he must get the puck deep to allow for the next line to establish themselves on the ice. He takes the open ice and crosses the blueline with both opponent defenders in front of him. Rather than just dumping it in the corner Kev decides he should probably get at least one SoG this week so he wrists a 72mph shot at the goalie from just inside the blueline. Unless he shot some heroin between periods the goalie gloves it easily and sets the table for the weakside D to start a breakout.
This is deemed worthy of 0.03 xGs.
1b) Cale Makar starts his shift in the OZ. MacKinnon wins the faceoff and the winger gets it back to Makar. Makar controls the puck and fakes sending it back down low to open up the middle of the ice. He walks the blueline as layers of traffic gather in front of his opponent's net. The goalie can't see the puck through the traffic and stands taller in his perimeter stance to try to find it. Makar sees this and sees an opening through the moving bodies. With no windup he wrists a 72mph shot from just inside the blueline. The shot is well placed and he scores under the goalie's glove. Goalie never saw it and curses his winger for missing his assignment and not blocking the point shot.
This is deemed worthy of 0.03 xGs.
2a) Ryan Lomberg takes a pass with speed in the NZ after some nice work by his other winger to win a high board battle. He has some room so he takes the defender wide and executes some respectable net drive by keeping his feet moving. He's by himself as his linemates are busy picking fleas off each other by the bench. He takes a contested shot along the ice from in tight to the net, the goalie has the angle covered easily and the shot bounces harmlessly to the corner.
This is deemed worthy of 0.3 xGs.
2b) Patrick Kane vacating his defensive responsibilities as he senses the puck is about to turn over creeps past the mouth breathing weakside defenseman still standing on the blueline trying to keep the pressure on. Sure enough Kane's center wins the puck along the boards and lifts a nice outlet area pass to center ice. Kane grabs the puck and is in alone on the goalie. He fakes going high glove and freezes our poor tender before making a move to the backhand and then crossbar down roofs it.
This is deemed worthy of 0.3 xGs.
Go ahead and handwave away these differences if you want but to me they are not reconcilable. It's not that xG models tell us nothing or aren't worth considering, it's that they are incomplete and aren't actually providing what they are claiming to. Over season long samples they can definitely be useful and predictive but stuff like the deserve-to-win'o'meter or NST's charting for individual games just isn't that useful without the context of seeing the game happen. It's not one or the other eye test vs advanced stats, it should be considering both as parts of an overall picture.
