THE World Indoor Championships get under way in Istanbul on Friday.
First Briton in final action will be Jessica Ennis, defending her pentathlon title. The battle between London's 2012 poster girl and Russia's Tatyana Chernova will be cut-throat and compelling, and possibly an Olympic wake-up call for Ennis.
Chernova last year relieved the Sheffield woman of the world heptathlon title in Daegu and margins between the pair are so slim that the outcome in Turkey may be determined up the home straight in the final event, the 800 metres, that evening.
This is more than an Olympic rehearsal. Significant psychological and bragging rights are at stake. Ennis enjoys the slimmest of edges indoors, but the javelin, added along with 200m for the heptathlon, plays strongly into Chernova's hands.
All of Britain is talking up our Jess, but it's time for a reality check.
Chernova, two years the Sheffield woman's junior and nine inches taller, is improving fearsomely fast. If Ennis cannot optimise undoubted long jump potential and, more pertinently, prevent a points haemhorrage in the javelin, Chernova is very capable of causing what we would do well not to characterise as "an upset".
The statistics show a 494-point improvement for the Russian over the past three years against 92 for Ennis who slipped back last year.
Year Ennis Chernova
2011 6790 6880
2010 6823 6572
2009 6731 6386
Ennis's highest point-scoring is in hurdles and high jump - remarkably given her 5ft 5ins. Her sheer speed is encouraging. Her 200m best is 0.45 better than five years ago, and her indoor hurdles has improved by 0.56sec to 7.87sec over eight years. But she has not matched her outright high jump best (1.95m) in almost five.
Chernova has improved her 200m speed by 0.55 in five years and in the hurdles by 0.62 in just four years, attacking Ennis in her best event and restricting her to a net hurdles dividend of just 35 points. In her best event, long jump, Chernova has added half a metre in five years, worth an extra 163 points. In that time Ennis has improved by 0.32m, worth 106.
Gains are small, but add up to the Russian nibbling away until she has surpasssed Ennis outdoors. She reckons it will take "around 7000" to win in London. That is a heptathlon barrier breached only by the retired Carolina Kluft in the past 20 years.
Compare the best indoor performances by Ennis and Chernova:
Hdls HJ Shot LJ 800m
Ennis 7.87 1.94 14.61 6.47 2:12.55
Ch'nova 8.02 1.86 14.54 6.72 2:10.10
Ennis's best pentathlon total is 4937 points, with which she won the world indoor title two years ago in Doha. That is just 54 points (the equivalent of 17 centimetres in the long jump) short of the 20-year-old world record. Chernova's best is 4855, also in 2010.
If both were to replicate all of the above indoor personal bests in one contest, Ennis would prevail by just 23 points, which equates to just over a second and a half in the 800m.
It's a margin so slim that it's calculated to keep athletics followers on the edge of their seats, and intensify Olympic anticipation this summer when the 60m hurdles is replaced by the 100m hurdles, and the 200m and javelin are added to complete the seven-event heptathlon.
Comparison for the heptathlon demonstrates the Russian has a bigger edge than that which Ennis has indoors. When Chernova took the world title in Daegu last year (6880 points) she was 57 ahead of Ennis's best (6823) which had landed European gold in Barcelona in 2010.
Their best outdoor performances look like this (Ennis first):
Hdls HJ Sh 200m LJ Jav 800m
12.79 1.95 14.67 23.11 6.51 46.71 2:07.81
13.32 1.87 14.17 23.50 6.82 54.49 2:06.50
If both athletes were to put all of their best performances together in the same contest, they would break the 7000-point barrier. Ennis would do better in four events to Chernova's three, but the Russian would win by 16 points, with 7053.
The damage in the 800m is a modest 19 points. The critical area is long jump and javelin – a swing to Chernova by 102 and 152 points respectively.
When Ennis surrendered world gold in Daegu, long jump and javelin earned her 1706 points to Chernova's 1960. Game over.
Expect an action replay in London if Ennis fails to address these deficiencies.
Chernova has genes, age, physique, and the legacy of the Russian system on her side. She lives with her parents in Krasnodar, despite having been rewarded with a government apartment for taking Olympic bronze in Beijing.
With Ennis absent through injury, and a positive drug test disqualifying her friend, Ukrainian Lyudmila Blonska, Chernova was upgraded from fourth.
Chernova uses her flat merely to store her wardrobe. Her father and coach, Sergey, is a former decathlete. He cooks her meals at the family home, gives her massages, and finds time to be minister of sport for an area which includes Sochi, venue for the 2014 Winter Olympics.
Her mother, Luydmila, ran for the Soviet Union in the 1980 Olympics, in the heats of the 4 x 400m relay. In those days, a medical certificate was required if an athlete who had contested heats was unable to run in a final.
The Soviets produced not one, but two, drafting in women who had placed fourth and fifth in the individual 400m. Though dropped, Chernova's mum collected gold when the Soviets won.
No such certificate would be needed today.
Ennis may just savour Turkish delight this weekend, but this is merely the hors d'oeuvre to a main course in which she can't afford to get any ingredient wrong.