Serena and Venus Williams [ Images ] both booked their places in the third round of the Sony Ericsson Open with victories at Key Biscayne in Miami [ Images ] on Saturday.

World number one Serena did not sparkle but still had little trouble in her 6-2, 6-3 victory over compatriot Alexa Glatch.

Having dealt with the 19-year-old Californian, a wildcard entry, Williams will now play China's Peng Shuai [ Images ], seeded 32nd, who beat Italian Mara Santangelo 7-5, 6-3.

Williams, who is seeking her sixth win at the Key Biscayne event, was far from happy with her performance.

"I definitely think I could have played better. But I had a few little jitters going out there -- no one wants to go out in their first match," she said.

Serena's sister Venus got off to a slow start but found her form to defeat spirited Israeli Shahar Peer 6-3, 6-3 and ensure a meeting with German Anna-Lena Groenefeld in the next round.

In the men's event, fourth-seed Andy Murray [ Images ] had to graft for his 4-6, 6-3, 6-2 win over Argentine Juan Monaco.

The Scot had his serve broken twice in the first set and then faced a 0-40 deficit in the first game of the second set, but fought back to hold his serve and then took a firm grip on the match.

"The only thing that matters really is winning," he said. "If I played great today and lost then I'm sure everybody would be pretty negative about it.

"I was really happy with the way I served. I thought that was just the key. I served a high percentage and got a lot of free points. When I really needed it in the second and third set then I found a big serve," he added.

"It's something in my game that's improved. I have to work on the rest of my game but I'm just happy I've got the chance to do that. I could have lost today," said the 21-year-old.

Murray will play Chile's Nicolas Massu [ Images ], a three-set victor over American Mardy Fish [ Images ], in the next round.

Another American Sam Querrey was knocked out by Spain's Feliciano Lopez [ Images ] 6-7, 7-5, 6-2, the number 32 seed firing 15 aces and breaking serve three times to set up third-round tie with compatriot Fernando Verdasco [ Images ].

Eighth seed Verdasco defeated German qualifier Benjamin Becker 6-3, 6-4. The Spaniard lost his own serve three times but converted five of eight break point opportunities on Becker's serve.

Later, world number one Rafael Nadal [ Images ] opens his campaign against Russia's [ Images ] Teimuraz Gabashvili. In the women's event, Serbian third seed Jelena Jankovic [ Images ] is up against Argentine Gisela Dulko [ Images ].