Alexander spent nine years as a player at Deepdale before a spell as caretaker manager and saw substitute Ball curl home an 85th-minute effort to deny title-chasing Preston a victory that would have put pressure on League One leaders Bristol City.
Daniel Johnson had given the hosts an early lead at Highbury in a keenly contested derby, when he took control of a loose ball outside the area and curled a strike past Chris Maxwell.
Preston proceeded to dominate the remainder of the half and started the second period well, before Paul Huntington came off worse in an innocuous penalty box collision with Maxwell.
The former Newcastle United defender was later confirmed to be sitting up and talking, having been taken off in a brace, with Fleetwood going on to claim a share of the spoils.
Ball did well to work himself some space outside the area and lofted a looping effort over Sam Johnstone to stop Preston moving within seven points of Bristol at the summit.
