Plenty at stake for all teams
Things are relatively clearer in Group A than in B, since only two matches are left, and they'll both be played in Chennai, a venue which is less likely to get affected by the weather. With two games to go, four sets of results are possible. Here's a look at which teams will go through in each case.
Matches left: Cape Cobras v Trinidad & Tobago; Chennai Super Kings v New South Wales
Scenario 1: Cape Cobras and Super Kings win
This is a simple case in which Cobras and Mumbai Indians will be the only two teams in the group with five points, and will go through to the semi-finals.
Scenario 2: Cape Cobras and NSW win
NSW will move to the top of the table with six points, while Cobras and Mumbai Indians will be level on five. Cobras have a much better net run-rate, and will hence make the cut at the expense of Mumbai Indians.
Scenario 3: T&T and Super Kings win
Mumbai Indians will be the clear leaders with five points, while three teams will be tied on four. Among these three teams, T&T have the best net run-rate at present, since their two losses have been such narrow ones. However, Super Kings aren't as far behind as it might appear on the points table: if they score 140 and win by, say, 25 runs, and if T&T win by a run, Super Kings' net run-rate will be marginally better than T&T's.
Scenario 4: T&T and NSW win
NSW and Mumbai Indians, with six and five points, will go through.
The rain factor
If the match between Cobras and T&T is washed out, then T&T will finish with three points and surely be knocked of the tournament. Cobras will finish with four (and a net run-rate of 0.443), and their progress will depend on the result of the last match. If NSW win, they will progress with Mumbai Indians, but if Super Kings win, three teams will be tied on four points, with Cobras almost certain to have the best net run-rate among them.
If the second match is washed out, then NSW will join Mumbai Indians on five points, and will go through if T&T have beaten Cobras in the first game. However, if Cobras have won, they'll go up to five points and edge ahead of Mumbai Indians on net run-rate. In that case, Cobras and NSW will progress.
If both games are rained out, then Mumbai Indians and NSW will make the cut.
S Rajesh is stats editor of ESPNcricinfo. Follow him on Twitter