The American seventh seed looked down and out when she collapsed in agony on the Centre Court turf at 5-5 in the second set, having roared back from 5-2 down.
Crying with frustration and screaming in pain Williams needed lengthy treatment before hobbling on to reach a tiebreak when rain came to her rescue at 4-2 down.
When play resumed nearly two hours later Hantuchova finished off the tiebreak with three successive points but Williams was not about to give up without a fight.
A bad-tempered Williams began to move more freely and with Hantuchova seemingly strangled with nerves, the 2002 and 2003 champion surged into a 5-2 lead.
She brought up a match point with a belting drive volley and ended the contest when a bemused Hantuchova netted a backhand.
