out of their shell

[Kontol]

What is the meaning of the phrase "out of their shell" in this sentence?

74 mins: Everton are finally out of their shell. Townsend feeds Gordon, who can’t make it past his marker on the left. City break and Palmer goes for the 30-yarder, but he is evidently no Rodri and the shot is wild.

 

[probus]

I'm not a football fan but my guess is it means Everton had been playing purely defensively but have at last gone on the attack.

 

[jutfrank]

They're starting to put together some attacking moves, after being penned in by City.