The SERENA Factor in Miami (by Harvey Fialkov)

Serena Williams has been a force to be reckoned with at Key Biscayne. What happens now?

The road to the Sony Ericsson Open women's championship got a lot easier when Serena Williams withdrew with a knee ailment last weekend. Williams is 52-6 in Miami. She has won five of the last eight Sonys and made the finals six of the past seven times she has been entered at Key Biscayne. After winning three of the last five majors, including January's Australian Open for her 12th Grand Slam title, Williams was a clear-cut favorite to surpass Steffi Graf's record of five titles in Miami and tie Andre Agassi's all-time mark of six.

So, with five former No. 1s still in the draw, including Serena's big sister Venus, the women's bracket seems tough to predict. What does it mean to the field — also missing injured Russians Maria Sharapova, a two-time finalist here, and third-ranked Dinara Safina — to have Serena Williams out?

Chinese duo on rise: Li Na and Jie Zheng became the first Chinese women to reach the semifinals of the same Grand Slam at the same time at the Australian Open. Although they have five singles titles between them and Jie has two major doubles titles, no one from their country has won a premier event like the Sony Ericsson Open.

Serena factor: The two top-20 women are a combined 1-8 vs. Serena. Li reached a career-high No. 10 after the Aussie, where she was knocked out by Serena. And Jie was the first Chinese woman to reach a major semi at the 2008 Wimbledon, where she was also booted out by Serena. On Serena's way to the final at Key Biscayne last year she took out three straight Chinese women, including Peng Shuai, Jie and Na in the quarters.

Belgium basher is back: Justine Henin, a seven-time Grand Slam champion with 41 titles, returned this year after walking away at the top in May 2008, citing fatigue. She returned with a vengeance in January, reaching the finals of Brisbane and the Australian Open before losing her first match at Indian Wells. Henin and her sweet one-handed backhand mean trouble for somebody.

Serena factor: Was it a coincidence that Henin quit one tournament after the much stronger Serena wiped her out 6-2, 6-0 in the Miami quarters? It was Serena who deprived Henin of a title here when she fought off a bagel set and two match points down to beat her in the 2007 final. And guess who dispatched the diminutive slugger in this year's Aussie final?

Venus may be rising: There's no hotter player on the tour than Venus, who before skipping Indian Wells as usual won three straight events. Venus is 14-1 with titles in Dubai, Acapulco and an exhibition victory over Kim Clijsters in New York. She's rested and eager to win her fourth Miami title, but first since 2001.

Serena factor: Big sis has always hated beating baby sis. Although Venus won the 1999 title here in the first all-sister WTA Tour final, she was knocked out of the 2002 and 2009 semifinals by Serena – to whom she has lost four straight times.

Serb rebounds: Jelena Jankovic, who finished 2008 at No. 1 despite not winning a major, dropped to No. 8 after 2009 without getting past the fourth round of any major. She's crediting Nick Bollettieri protégé coach Chip Brooks and a less-muscular frame for her resurgence at Indian Wells, where she won the most prestigious title of her career Sunday and first in seven months despite entering the tournament with a 5-4 record

Serena factor: Sure, Jankovic is a respectable 3-4 against Serena, but lost the last two meetings in big tournaments in 2008. In her only Grand Slam final appearance at the U.S. Open, Jankovic fell 6-4, 7-5. Five months earlier, Serena needed eight match points to finish Jankovic in the Miami final. "It's like a heavyweight champion, and I'm a feather champion, you know? I cannot match up against her,'' Jankovic said after the match.