Two players with identical ability can perform differently depending on how long their inputs take to reach the screen. That delay is measurable and it constrains what either can do.
The delay is a chain, not a single number
A press travels through the controller, the console, the game engine, the network and finally the display, and each stage adds time. None of the individual delays is large, and the sum of them is.
The total is what the player feels, so improving one stage while ignoring another produces smaller gains than expected.
Competitive setups are built by shortening every link rather than optimising the one that is easiest to change. A wired controller attached to a slow television is still a slow setup.
Displays are the most commonly overlooked link
Televisions apply processing to improve picture quality, and that processing holds each frame briefly before showing it. Motion smoothing and noise reduction both need to see frames before they can alter them.
A low-latency display mode disables most of that processing, which is why competitive players use it despite the flatter image.
The difference between a processed and unprocessed picture is large enough to matter for timing-sensitive actions.
Timing windows are where lag becomes visible
Football games judge actions such as tackles and finishes within short windows after an animation begins. Press outside the window and the animation resolves without the input having any effect.
Added delay does not remove those windows but shifts when the player must press relative to what they are seeing.
Players adapt by pressing earlier, and inconsistent delay is worse than consistent delay because adaptation cannot settle.
Network conditions add variance rather than offset
Online matches introduce transmission time and server processing, both of which fluctuate rather than staying fixed. Distance to the server sets a floor, and congestion moves everything above it.
Games compensate by predicting inputs locally and reconciling with the server, which keeps play smooth but can rewrite what appeared to happen.
That reconciliation is the source of outcomes where a challenge looked won locally and resolved differently once the server agreed. The player sees the ball change hands after the fact, which reads as unfairness rather than as arbitration.
Offline events change the game being played
Local area finals remove the network stage entirely, leaving only hardware delay, which is small and stable.
Players who qualified online sometimes find their timing recalibrated at an offline event because the delay they trained against is gone. Habits built to compensate for lag become overcorrections once the lag disappears.
The competitive discipline and the online version are therefore not quite the same game, and the difference is measured in milliseconds nobody can see.