Serena Williams made a winning return to the WTA tour but needed three sets to get past Bernarda Pera at the Lexington Open.
The number one seed, who was last in competitive action at a Fed Cup qualifier in February, lost the first set in Kentucky.
Pera had two opportunities to earn a decisive break against the 23-time grand slam winner in the next set, but on both occasions Williams fought back and eventually levelled before she hit top gear to win 4-6 6-4 6-1.
"I wasn't in a good rhythm and I just kept thinking Serena, play like you've been practising," Williams told wta.com.
"I knew I could play a little bit better if I just hung in there."
Williams will face sister Venus Williams or former world number one Victoria Azarenka in the second round and is using this tournament as preparation for the US Open, which begins on August 31.