Serena Williams battled early nerves but has commenced her US Open farewell campaign with a first-round victory over Danka Kovinic in front of a loud Arthur Ashe Stadium crowd on Monday.
The 23-time major champion, who is expected to end her decorated tennis career after the Flushing Meadows tournament, triumphed in one hour and 39 minutes over the unseeded Montenegrin 6-3 6-3.
Williams will face a bigger test next on Wednesday against second seed Anett Kontaveit who eased past Jaqueline Cristian 6-3 6-0.
Given Williams' impending retirement, there was a sense of expectation but also trepidation inside the star-studded center court and the 40-year-old appeared nervous early on with two double faults in a row in the first game.
But after a topsy turvy first set that included five breaks of serve, Williams eventually got a hold of the contest.
Williams improved as the match wore on, hitting 23-18 winners.
Kovinic won three games in a row after Williams led 2-0 early, but the American responded in the sixth game to break back to square it up and she never looked back.
Williams was forced to save four break points in an epic service game before converting set point after back-to-back aces.
The six-time US Open champion broke Kovinic in the fifth game of the second set to assert her control on the contest, before clinching the match by breaking to love.
Data slam: Serena's durability on show
This year's US Open marked Williams' 21st campaign at Flushing Meadows and she maintained her perfect first-round record with Monday's win over Kovinic, extending her run to 21-0.
Williams debuted at the US Open in 1998 and won her second career major there in 1999. Her durability is highlighted by the fact that Monday's win means she became the fourth player in the Open Era to win a grand slam match in her teens, 20s, 30s and 40s after Martina Navratilova, Kimiko Date Krumm and sister Venus Williams.
Kovinic – 18/25
Williams – 23/25
Kovinic – 6/8
Williams – 9/6
BREAK POINTS WON
Kovinic – 2/10
Williams – 5/11