At what point in the game do teams make substitutions?

I wrote about substitutions a few weeks ago with regards to substitutions last season in the Premier League. I’ve decided to expand on these slightly by taking a look at the state of the game when the substitutions are actually made. The following data is taken from Premier League fixtures from the 2010/2011 season.

The following chart shows the three states that the game can be in when a substitution can be made. A side can be winning, drawing or losing. Unsurprisingly most substitutions are made whilst a side is losing, in fact 13% more subs are made by clubs when they are losing than when they are winning.

The next chart shows something a little more interesting. It displays the number of substitutions made in the Premier League at different stages of the game, when sides are winning by 1, 2, 3, 4 or 5 goals, when they are losing by 1, 2, 3, 4, 5 goals and when scores are level. What’s perhaps most interesting is that when sides are losing by a goal or two goals then they are more likely to use substitutions than if they are in the equivalent winning position, however if a side is losing three nil they are less likely to use substitutions than if they are in the equivalent winning position.

I believe that this fact is due to a couple of factors, firstly it’s unlikely a manager will be able to change a game with substitutions if his side is losing by three goals and secondly (and perhaps most importantly) it’s likely he will have already used up his substitutions when his side were losing by a goal or two. It’s probably also worth mentioning that managers love to tinker with their side when they go three or four goals up, allowing their star players to have a few minutes rest or to blood youngsters.

I’m not sure that these charts and statistics show anything meaningful or insightful but they may give an indication as to when subs are most likely to be used.