go into one's shell
verbEtymology From turtles, who go into their shells to protect themselves.
1
Idiomatic To act defensively.
- Instead of gathering the ball, De Gea poked it away with his foot and Streller was able to place a powerful half-volley into the net. United went into their shells and it was not until the 29th minute that they mustered a response - one from which they should have equalised.2011 December 7, David Ornstein, “FC Basel 2 - 1 Man Utd”, in BBC Sport: