One of the favourite cliches of coaches is this: "There is no 'I' in 'team'." But if the history of sport teaches us anything, it is that the fortunes of certain sides revolve around the form and fitness of one man. With quarterback Peyton Manning's golden arm directing proceedings, the Indianapolis Colts were perennial Super Bowl contenders. Having lost him to a neck injury, they are 0-13 this season.
Sri Lanka won Muttiah Muralitharan's farewell Test in July 2010, thrashing the world No 1-ranked Indians by 10 wickets. Since then, they have rarely had a sniff of success. In 15 Tests without Murali, they have picked up 20 opposition wickets just twice. The first of those, against Australia in Galle this year, was lost by 125 runs after some inept batsmanship.
At Centurion, on a bowler-friendly surface, the top score was Angelo Mathews' 38. Post-Murali, they have been bowled out for less than 200 seven times, losing series at home to Australia, away to England and in the UAE to Pakistan.
It is hard to establish a direct link between the retirement of an all-time-great bowler and batting implosion.
But the lack of bowling potency has meant that it is mandatory for the Sri Lanka batsmen to pile up big totals.
Even on home pitches where they have traditionally prospered, the batting has failed to build up the scoreboard pressure that a bowling line-up, lacking both experience and nous, needs to force mistakes.
It does not help that their two finest batsmen are so much more accomplished in familiar conditions. Kumar Sangakkara's average at home (62.06) is conspicuously better than the away figure (47.33), and the disparity is even starker in the case of Mahela Jayawardene (62.92 at home and 40.95 away). Thilan Samaraweera's average also drops nearly 16 points away from home.
Those figures help to explain why Sri Lanka have never won a Test in Australia, South Africa or India. The contrast with India's batting titans is telling. Rahul Dravid averages more away (54.71) than he does at home (51.35), while Sachin Tendulkar's numbers are almost identical (56.37 at home, 55.74 away). Between them, Sangakkara and Jayawardene have 20 overseas hundreds. Dravid has 21. Tendulkar's tally is an astonishing 29.
Sri Lanka have also been the victims of itineraries that are hopelessly skewed in favour of a "big four" - India, Australia, England and South Africa. The loss at Centurion was their first game in South Africa since January 2003. India have toured the southern cape twice since then. Australia have come and gone thrice.
Between them, Jayawardene and Sangakkara have played 230 Tests. Of those, only 38 caps have come in Australia, South Africa or England - circumstances that ask the most questions of a batsman's technique. Tendulkar has played 48 matches in these countries.
Step-brotherly treatment aside, Sri Lanka's fortunes have also plummeted because there is not much batting talent coming through. Upul Tharanga was once heralded as the next big thing but has not played a Test in four years. Dinesh Chandimal's inconsistency in the 50-over arena has retarded his progress into the Test side, while Lahiru Thirimanne has yet to make a spot his own. Of the young talent, Mathews - who has struggled with injury recently - looks the most gifted.
Sri Lanka's selectors also need to be questioned for not trusting in Ajantha Mendis and his mystery deliveries. At Centurion, they had South Africa in trouble at 173 for five, only for the lower order to turn the game in the company of AB de Villiers. Tail-end batsmen usually do not handle spin well, and South Africans even less so. It is something to ponder as a battered Lankan side heads to Durban for the Boxing Day Test.
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