back line

Battling Bolton disputed the goal, claiming Drogba was offside, but the Ivorian appeared to have timed his angled run across the visitors back line to perfection to race onto a fine Michael Essien pass and ensure Chelsea moved back into fourth place in the Premier League.

A running fullback radically improves the attacking prowess of any back line, particularly if she is able to read a play, knowing when it's time to hit the line at pace or to join the line to act as an extra attacker.