I’ve always been fascinated by the things clubs do to give their teams an extra edge. It’s not just in soccer; there are numerous examples of baseball, basketball, and American football clubs using everything from locker room heating to air flow in the stadium to hamper the opposition. And so I came to consider that humblest of soccer moments, the throw-in.

A throw-in is, of course, just another kind of pass. Opposing teams defend them particularly avidly in their own half of the field, but attacking teams usually have routine to ensure a completion. If an attacking team is particularly well drilled, it should be able to complete a throw-in relatively quickly after the ball has gone out of bounds. If not, it may need more time, and that’s when panic can set in.

Not surprisingly, if we look at all throw-ins in the attacking half by the number of seconds (rounded down) before taking them, there’s a clear trend:

Needing more time to make a throw is a bad sign. The offense may be disorganized, or the defense may be marking particularly closely. A bigger delay from the time of the ball going out to the throw was correlated with a lower completion rate in the English Premier League in 2013-14.

At the team level, the relationship was less clear. There were some big differences in delays and completions, suggesting tactics were quite heterogeneous as well:

Several teams achieved a high completion rate regardless of their average delays. But Crystal Palace took a long time and still performed poorly, while West Ham wasn’t hurt much by an even longer delay.

Though all this was interesting enough, I wanted to know how teams fared when facing the same opposition home and away. Specifically, I was interested in the ball kids. That’s right – I wanted to know if those boys and girls took a little longer to give the opposition the ball. An extra second or two would give the home side time to organize its defense, a minor but useful edge.

A simple way to investigate this idea would have been to look at the differences in the delays for home teams and away teams by venue. But if a team defended throw-ins especially well at home (or the opposition was especially distracted by noisy fans), then it would be hard to separate the effect of the ball kids. Instead, I decided to look at how the delays varied when teams faced the same defense in different stadiums.

For each team, I compared opponents’ delays in taking throw-ins at home and on the road. Again, a team that defended better at home would be indistinguishable from one whose ball kids took their time in giving the opposition the ball. Yet according to the first graph above, a team that defended well would also allow a lower percentage of completed passes. So the question was clear: Which team generated the biggest delays for opponents in its own stadium without holding them to a lower completion rate?

These were the results:

Every team generated a bigger delay for its opponents at home than on the road. For Manchester City and Manchester United, the difference was almost two seconds. But both of those clubs also held their opponents to much lower completion rates at home. So there were three possibilities: 1) the longer delays were solely the result of aggressive defending; 2) the delays were solely the result of ball kids’ actions and they were effective in reducing completion rates; or 3) the delays stemmed from a mix of the two factors.

This was not the case at Newcastle United, Stoke City, and Crystal Palace. When playing at home, all three forced their opponents to delay throw-ins by at least an extra second – and yet they barely affected their opponents’ completion rates. Here it seems unlikely that the longer delays came from strong defending at home. Yet it also seems unlikely that the delays were effective. Using these data, I can’t identify a team that generated effective delays without qualitatively better defending.

Indeed, there’s always the possibility that the three clubs above would have allowed higher completion rates at home than on the road, and thus the virtually unchanged completion rates meant that the added delays were effective. But what teams might have defended worse at home? Perhaps the ones that attacked all-out to put on a show for their fans – Newcastle and Crystal Palace might have fit that bill, but Stoke City probably didn’t.

So were the ball kids at Stoke delaying deliberately? Not necessarily. There might simply have been fewer of them around the field than at other stadiums, or they might just have been a little slower by nature. Either way, I think throw-ins deserve more attention, since they’re repeatable situations where one team can directly constrain another team’s options.