Australia's series loss to a low ranked Sri Lanka - currently at No. 7 in the ICC Test rankings - has meant that it is highly likely that the No. 1 spot changes hands by the end of this month.

According the ICC rankings methodology, the penalty of losing a series to an opponent that is rated low is more than if the opponent were rated higher. For example, if Australia had been playing a similar three-match series against India (who are at 112 points as opposed to Sri Lanka's 85), a 0-3 loss to them would've robbed them of about six points. A 0-3 loss to Sri Lanka, however, is going to cost Australia nine points, bringing down latter's ratings to an approximate 108 points. Australia's obvious weakness in the subcontinent, or Sri Lanka's relative strength at home, does not have any bearing on how the ratings are calculated since the ICC methodology doesn't differentiate between home and away conditions.

The erosion in Australia's ratings gives other teams that weren't too far behind the opportunity to make a grab at No. 1. England, Pakistan and India are all in with a chance of topping the rankings following their ongoing series. Here is how each of the current top four could end up at No. 1.

Australia: They have to win the Colombo Test to have any chance of retaining their No. 1 ranking. Either England - with a win in the Oval Test - or India - with a 3-0 margin against West Indies - could topple them. Australia can hang on to their top spot even if the Oval Test is drawn and India don't win by a 3-0 margin.

India: A draw in Kingston means that India have to win their remaining two Tests against West Indies to take the No. 1 spot. A 3-0 margin will bump them up to the top irrespective of results in the other series.

England: A 3-1 series win against Pakistan will give them the No. 1 ranking provided India don't win by a margin of 3-0 against West Indies. Even a draw in the Oval Test can give them the top spot if Australia don't win the Colombo Test and India win only one of their remaining two Tests against West Indies.

Pakistan: They have to win the Oval Test and hope India don't beat West Indies by a margin bigger than 2-0 and Australia don't win the Colombo Test.