Maria Sharapova shook off the rust to beat Japan's Ai Sugiyama 6-4, 6-7, 6-1 in the first round of the Stanford Classic on Monday.
Fellow Russian Elena Dementieva joined her in the second round after beating Britain's Anne Keothavong 6-1, 6-4.
On the comeback trail after shoulder surgery last year, three-times Grand Slam champion Sharapova conceded she needs more matches to get her form back.
"I had so many chances to close out the match and I didn't," the 62nd ranked Sharapova said. "I couldn't raise my level when had to. But in the third set I didn't do anything wrong, I was steady and kept doing the right things."
After winning the first set, Sharapova squandered a 5-2 lead in the second and was unable to cash in on two match points leading 6-4 in the tiebreaker, double faulting and committing a backhand error.
The Japanese player moved ahead with a scalding backhand winner and then took the tiebreaker 8-6 after Sharapova dumped a backhand into the net.
However, the former world number one turned it around in the third set with huge groundstrokes and aggressive returns to put the game away against her 34-year-old opponent.
Dementieva said she was still adjusting to jetlag, but was pleased with her play. The world number four is setting her sights on a US Open title run.
"I hope it's going to be a long summer," Dementieva said.
"I need to play some good matches to get my confidence for New York."
Seventh seed Agnieszka Radwanska of Poland also moved ahead with a 6-0, 6-1 demolition of Romania's Sorana Cirstea.
Top seed Serena Williams will take the court on Tuesday against China's Li Na while her sister Venus faces Canadian wildcard Stephanie Dubois.