Jessica Ennis was in fine fettle when she competed in 60 m hurdle final during Aviva Grand Pix [GALLO/GETTY]

The prelude to one of the big clashes at the London Olympics will be played out during Friday's opening day at world indoor championships when defending champion Jessica Ennis faces off against Tatyana Chernova in the pentathlon.

The two will compete in five events in one day, deciding who gets the bragging rights going into the Olympic heptathlon.

In the only other gold medal event on Friday, Reese Hoffa will be seeking a second gold medal in the shot put after winning in 2006, and to extend the U.S. domination of the event.

In the heats of the 3,000, Ethiopian great Meseret Defar sets off on her quest to become the first female athlete to win five world indoor gold medals in a row.

"This world championship is very special to me,'' Defar said Thursday.

"I expect to win again.''

Defar, too, sees her race her as a vital preparation for the Olympics, where she will be trying to win back the gold medal she took at the 2004 Athens Games before finishing with bronze in Beijing four years later.

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All eyes in Britain will be on Ennis, though.

She won the 2009 world heptathlon title in Berlin and added the indoor pentathlon a year later, making her a pre-eminent home star for the London Games. A surging Chernova, though, reached the pinnacle of the multi-event discipline in Daegu, South Korea, last year when she edged the Briton for gold in the outdoor seven-event heptathlon.

The world record has been at 4,991 points for 20 years and many feel the rivalry may be enough for one of the two to break the 5,000-point barrier.

"This is a dream for all sportsmen to break a world record,'' Chernova said, adding she was confident they would at least get close to the mark.

Another one who could get close is Sally Pearson, the in-form hurdler who added a sterling early season to a world title and election as woman athlete of the year in 2011.

The Australian won the national Olympic trials in 12.49 seconds on a wet and miserable weekend in Melbourne, the fastest time ever for a 100 hurdles on Australian soil. No woman has ever run a faster hurdles race this early in the year.

So, it is only logical she has a good shot at the 4-year-old 60 hurdles world record of 7.68, held by Susanna Kallur of Sweden.

"My body is just ready to run fast,'' said Pearson, who rarely races indoors.

"I have no idea what I am going to run out there."

Besides the shot put, the United States will also be looking for a great start in the 400 from Sanya Richards-Ross, who has the best two performances of the year. Aleksandra Fedoriva of Russia looks like her closest challenger, just as the Russians will be to the U.S. team in the 4x400 race, too.

In the men's sprint, it will likely turn into another U.S.-Jamaican duel.

Lerone Clarke has been on a roll coming into Istanbul and had the world's fastest 60-meter time until Trell Kimmons went to high altitude and ran 6.45 seconds in Albuquerque, New Mexico, to knock .02 off the mark.

Stars like Olympic champion Usain Bolt and world champion Yohan Blake traditionally skip the indoor season.