Serena Williams showed no sign of knee trouble as she began her quest for an eighth Miami Open title with a 6-3 6-1 win over Monica Niculescu.

The world No.1, who had battled past the Romanian in her opener at Indian Wells, was later forced out of the tournament in California with a knee injury, forfeiting her quarter-final match there eight days ago.

“It was a little sore in practice, but it was OK today,” Williams said of her knee on Saturday (Sunday AEDT).

“I really didn’t feel it today, to be honest.

“Once you step out on the court you have so much adrenaline going. The adrenaline kind of kills it. So I was surprised. I felt pretty good.”

The 33-year-old Williams next faces 15-year-old Catherine Bellis.

The American teenager, nicknamed CiCi, advanced with a 6-2 6-1 win over 29th-seeded Zarina Diyas on Friday, when Williams’ match was among those washed out by rain.