winners to reach 30-40.
Williams broke serve to lead 1-0 after Lucic-Baroni sent a down the line backhand wide.
The American opened her first service game of the match with an ace before striking a down the line forehand volley winner to lead 30-0. A Lucic-Baroni forehand hit long followed by another forehand netted sent Williams ahead 2-0.
Both players held serve as Williams led 3-1.
With Lucic-Baroni serving, the American hit a crosscourt forehand volley winner followed by a backhand down the line winner to reach 30-40.
However the Croatian struck an ace down the tee; her fourth ace of the match, to ruin Williamsí chance to go ahead 4-1 by leveling the score at deuce.
Another Lucic-Baroni ace out wide followed by a backhand volley winner down the line from the Croatian on gamepoint put the score at 3-2.
In her following service game, Williams netted a forehand and a backhand to fall behind 0-30. Lucic-Baroni then hit a crosscourt forehand winner to lead 40-0. Williams netted a down the line forehand to drop serve as Lucic-Baroni broke to level the set at 3 all.
The set remained on serve with Williams serving down 4-5.
A Lucic-Baroni forehand down the line return winner followed by two Williams crosscourt backhands hit wide put the American down 0-40.
The Croatian only needed one setpoint as she powered a backhand down the line which forced Williams to strike a crosscourt forehand long as Lucic-Baroni took the set 6-4.
Three holds of serve to start set two saw Williams serving down 1-2.
The American went ahead 40-15 after striking an ace out wide. However several groundstroke errors from Williams saw the game reach three deuces before Williams netted a crosscourt backhand to lose serve and trail 1-3.
Hitting with extreme pace from the baseline, Lucic-Baroni forced several groundstroke errors from Williams before striking a forehand down the line winner to hold serve and lead 4-1.
Williams held serve then broke serve to reach 4-3 following several baseline winners from the American.
However serving down 3-4,Williams netted two down the line forehands as well as a backhand crosscourt to trail 0-40. The American fought back to reach two deuces before netting a down the line forehand to drop serve and fall behind 3-5.
Two Williams forehand errors followed by a netted slice backhand return set up three match points for the Croatian.
Lucic-Baroni sent a serve out wide which Williams returned from the forehand side long to end the match after 1 hour and 23 minutes of play.
For the day, the 34 year old Williams had not played her best tennis, but the 32 year old Lucic-Baroni had played exceptionally well in some of her best tennis since being a promising up and coming teenager.