Now while the title might make you fall asleep, it’d be great if you could stay with me. Melbourne Heart took the unusual step of replacing their incumbent keeper during the middle of the season, replacing Clint Bolton with Andrew Redmayne, with the general consensus being that Redmayne, by the end of the season had become a useful keeper and was probably at a similar level to Clint (a consensus which makes sense by taking a look back at the numbers, both played roughly half the season each, Bolton conceded at a rate of 1.5 goals per game, while Redmayne conceded at a rate of 1.45 per game) however if you delve into it a little deeper, a stark difference between the two becomes obvious.
If we look at the graph that I produced last time, we can see Melbourne Heart was a fairly middling team in terms of the sucess of the defence to deny opportunities and in terms of our keepers ability to make saves. 
Figure 1. The goals conceded relative to the saves per goal ratio of each team over the entire A-League 2012-13 season.
So not too bad overall, not elite by any stretch of the imagination, but not really struggling. What if we extrapolate out the values for each of our individual keepers (presuming they kept up their current rate of saves per game and the number of shots on target per game remains constant a BIG assumption, but one that is true to the data we have so far) you can see a marked difference in the performance of our keepers over a simulated ‘year’.
Figure 2. The goals conceded relative to the saves per goal ratio of each team over the entire A-League 2012-13 season, including a seperation of the two Melbourne Heart goalkeepers for the season, Clint Bolton and Andrew Redmayne.
It becomes apparent that Andrew Redmayne firstly, made a lot more saves in total then Bolton had to make in the first half of the season, but in addition to that, still conceded fewer goals and had a much higher saves to goals ratio, one which puts him essentially equal to Michael Theo from Brisbane Roar, ranked 2nd overall this season behind Ante Covic. The difference ends up being worth 8 goals, an awful lot in such a close A-League season. This isn’t to disparage the fine work done by Clint Bolton over the year, merely to observe that Andrew Redmayne faced a huge task in the second half of the season and he was most certainly up for it.
Given that the goalkeeper is by no means the only factor that effects the amount of goals conceded by a team, arguably the role of the central defenders plays just as big a role, Melbourne Heart used 4 different players in 5 different central defender combinations, the most common was Simon Colosimo and Patrick Gerhardt, with David Vrankovic filling in for good measure and Jamie Coyne making a cameo apperance as required, so if we consider the 3 main central defenders, what role did their different combinations have on our defence this year and did any of them make our keepers jobs substantially easier?
Well that’s another set of graphs for another day.
All Heart 