Tennis: With Serena and Venus Williams returning from injury and distracted by off-court activities, and Justine Henin-Hardenne and Kim Clijsters injured, the women's singles promises to be the most open in years.

Defending champion Serena may have been seeded number one, but defeats this season and burgeoning interests outside tennis mean questions remain to be answered.

She had surgery on her left knee last August, did not return to the tour until March and has not been in a major final since Wimbledon 12 months ago.

Venus last won a Slam in 2001 and, like Serena, has struggled with injury and lost in the quarter-finals of the French Open last month.

The draw means the Williams sisters, seeded first and third, could meet in the final for the third straight year, but they will not have it all their own way.

French Open champion Anastasia Myskina is the second seed, and is one of six Russians among the top seeds, but most attention will probably focus on 13th seed Maria Sharapova, who has all the ingredients to become Wimbledon champion according to coaching legend Nick Bollettieri.

The 17-year-old from Siberia, who reached the fourth round a year ago as a virtual unknown, won her first grass-court title in Birmingham last weekend and, according Bollettieri, has what it takes to succeed.

Sharapova, who plays Yulia Begelzimer of the Ukraine in the first round today, grew up at the famous Nick Bollettieri Tennis Academy in Florida .

"She's got everything she needs. With her mentality and background, she's going to do fairly well in every tournament," said Bollettieri.

"She's just got to learn how to adapt to the conditions, which she didn't do in France (she lost to Paola Suarez in the quarter-finals).

"She's capable of beating anybody but she's now one of seeds and other players want to beat a seeded player."

Meanwhile, men's champion Roger Federer does not know what to expect from Britain's Alex Bogdanovic when he walks out on Centre Court tomorrow.

Federer will open his defence against the unseeded 20-year-old left-hander, last week ranked 307th in the world.

However, the 22-year-old top seed is unsure what kind of reception he will receive when walking out at the famous old venue this afternoon.

"It is going to be interesting to see how the crowd will be, on his side or my side, I don't know," he said.

"But it does not really matter. For me it will be a very special moment and one I have been looking forward to for a long time."

Federer is all too aware of the fate suffered by 2002 champion Leyton Hewitt, who crashed out to giant Croatian Ivo Karlovic in the first round last year.

"For me there is a different kind of pressure, I feel," said Federer.

"Before, it was about making that first break through in the Grand Slam, to really go for the quarters or the semis. This time it is about defending that title - the focus is on me.

"I put a lot of pressure on myself also, when I step out on Centre Court, it is going to be strange."ORDER OF PLAY

(Number denotes seeding)

Centre court (play starts 1pm)

1-R Federer (Swi) v A Bogdanovic (Britain). 31-M Youzhny (Rus) v G Ivanisevic (Cro). L Kurhajcova (Slo) v 2-A Myskina (Rus)

Court one (play starts 1pm)

J Melzer (Aus) v 7-Lleyton Hewitt (Aus). M Gayanay Mikaelian (Swi) v 3-V Williams (US). 3-G Coria (Arg) v W Moodie (RSA)

Court two (play starts at noon)

C Castano (Colombia) v M Navratilova (US). J Boutter (Fra) v 6-J C Ferrero (Spa). 5-L Davenport (US) v D Randriantefy (Mada). D Tursunov (Rus) v 19-M Safin (Rus)

Court three (play starts at noon)

Amanda Janes (Brit) v 11-A Sugiyama (Jap) 10-S Grosjean (Fra) v T Ascione (Fra) 9-C Moya (Spain) v O Patience (Fra)