Many have praised Arsenal for getting a proven and experienced GK who makes Arsenal title contenders:
.@ChelseaFC's Cech could turn @Arsenal into genuine title contenders, writes @nicholaspwright http://t.co/wUbRSBpo4f pic.twitter.com/toT17QhJYg— Sky Sports Football (@SkyFootball) June 22, 2015
Then there are others like @footballfactman, (probably the best GK analyst in the blogosphere)
who is less excited:
@BobbyGardiner he's excellent in right set up. He was dire when AVBs high line exposed him pic.twitter.com/xrBjdQgVlO— Paul Riley (@footballfactman) June 22, 2015
My point here is not about Cech but GK's in general. They are voodoo.
I have ran a few scatter plots to show the linear regression of team save% over various lengths of time and none show any signs that a team or keeper is worth 'betting' on both in the short term or long term, at least when looking at saves per shot on target against (save%).
These results will be nothing new to most of you but reiterates that teams and GK's lack a lot of control over goals scored against them. Analytically, it is pretty tough to endorse keeper x, y or z. What we see one year or even for 2 yrs in a row (unlikely) can change very quickly.
Arsenal are not a poor club and can absorb this move without missing much of a beat, financially, but based on linear regression the best we can predict is that Arsenal will have a save% close to league average, in the 2015-16 season (like every other team).