How big an upset was West Indies' eight-wicket win in Mirpur?

West Indies went to Mirpur as a side most fans had filed under decline, a team better known lately for heavy defeats than for winning away. They came home from the first Test with an eight-wicket win that has been greeted as a jolt. The surprise is easy to understand, because our forecast before the match made Bangladesh 49% favourites at the Sher-e-Bangla National Cricket Stadium, with West Indies on 33%.

Yet this fixture has its own long history, and it runs the other way. Since 2009 the two sides have met 18 times in Tests, and West Indies have won 12 of them against Bangladesh's five.

Why the forecast favoured Bangladesh

Our ratings see two sides huddled together near the bottom of the men's Test table, close enough to hang their coats on the same peg: Bangladesh have a 35% chance of beating an average side on a neutral ground, and West Indies have 34%. With the teams that close, the pre-match call came down almost entirely to home ground, and a Test in Mirpur was enough to tilt it towards Bangladesh.

West Indies' Test form this year

The eight-wicket margin fits a side that has been turning a corner, slowly and unevenly. Last year West Indies were beaten heavily by India and New Zealand, the worst of it a 323-run defeat by New Zealand. This year they have won Tests against Sri Lanka and Pakistan, though Pakistan hit straight back in the next match.

Bangladesh have been just as erratic, beating Australia and then losing to them by an innings in the following Test. A home side that swings between those two results gives a forecast very little to hold on to.

What the second Test in Sylhet will settle

For the Test in Sylhet our forecast still leans to Bangladesh, at 48% against 36% for West Indies. That lean holds only as long as home ground keeps outweighing West Indies' long run of wins in this fixture, and Mirpur has just shown how thin that cushion is.

The win in Mirpur was an upset only on paper. Our forecast is right to keep Bangladesh slightly ahead in Sylhet, because home ground still counts for something between two sides this close, but the gap is far narrower than the Mirpur call suggested. West Indies go to Sylhet as the side this fixture's history favours, and a serious threat to win again.