dropshot, Williams sent a down the line backhand stab long to face breakpoint.
Williams then netted a crosscourt backhand to lose serve and fall behind 4-5.
Despite routinely delivering serves in the 70 to 80 miles per hour range, Erani raced ahead setpoint at 40-0 after Williams sent a crosscourt forehand return long.
A netted crosscourt backhand slice from Williams ended the set 6-4.
In set two, serving at 4 all, Williams committed two groundstroke errors before double faulting on
breakpoint to trail 4-5.
However with Errani serving for the match only two points away at 6-4, 5-4 30-15, Williams hit an overhead winner, followed by a down the line backhand winner and a down the line swing forehand volley winner to break serve and level the set at 5 all.
Both players held serve to reach a tiebreaker which the American then took following more powerful baseline play.
With the match on serve in set three at 3 all, Williams stepped up her level of play once again to take the last three games of the match to win 4-6, 7-6(7-3), 6-3.
Williams had held serve at love then broke serve at love to end the match and put the Americans ahead 2-1.
However the American team then lost both their fourth singles match and their doubles match to fall 3-2 to Italy.
Williamsí older sister and frequent doubles partner Venus Williams had withdrawn from the meet for personal reasons which forced the USA to play a weaker doubles team of Serena Williams and Alison Riske in the decisive fifth match which the Americans lost to Errani and Flavia Pennetta 6-0, 6-3.
Italy returns to the World Group and will compete for the Fed Cup trophy next year while the Americans are relegated to World Group II.