Substitute effects and the dangers of hyping up Alexey Miranchuk's per 90 stats

I tried to make this title sound more academic than the rest of the piece will actually be

“I would say that we are back, baby.” 

Garth Lagerwey began his post-Alexey Miranchuk signing interview on 92.9 with…”We’re back.” 

That’s a helluva statement. I don’t know how tongue-in-cheek it actually was, but either way we can go ahead and chalk it up as Lagerwey rubber-stamping this signing as a no-doubt, slam dunk, sure thing. Sure as the sun rises in the East or that Atlanta United will get bounced from the Leagues Cup group stage, Miranchuk will be the top-five-at-their-position-caliber No. 10 that was promised. He’ll have to be if “We’re back” carried any truth to it. 

We won’t know until we know of course whether or not any of that’s true. The bottom line with any signing other than Lionel Messi is that you’ll never, ever know for sure whether a player’s success or lack thereof elsewhere will translate to MLS. However, on the surface, Miranchuk’s statistics paint a picture of the sure thing Lagerwey is talking about. 

“Miranchuk is an elite chance creator,” Lagerwey said. “One of the, literally, one of the top guys in all the top five leagues in Europe combined. “We're talking about top five guys in goal contributions, so goals plus assists for 90 minutes. You know, tops in terms of expected assists, tops in terms of key passes.”

There are no lies there. Per FBref, Miranchuk finished in the 98th percentile in non-penalty xG per 90 among attacking midfielders and wingers in Serie A last season. He finished in the 98th percentile in assists, the 98th percentile in expected assists, the 99th percentile in non-penalty xG plus expected assists per 90 and the 99th percentile in shot-creating actions. There’s no denying the fact that his per 90 numbers are outstanding. This? This is gorgeous.

But how real is it? 

Substitute Effects

In soccer analytics, there’s a simple idea known as the substitute effect. It’s one of those analytics things that actually lines up with an obvious eye test thing. Players who come on later in games as an attacking substitute are more likely to see a boost in their per-90 attacking statistics. Attacking subs come on in situations that require teams to, ya know, attack. They’re coming in on fresh legs. Playing in the most attack-minded minutes of the game as one of the few players who hasn’t been running around for the previous 70 minutes is going to provide a lift to a player’s per 90 statistics in comparison to when they actually play a full 90. This is one of those things you don’t have to overthink to understand.