England v Sri Lanka, World T20, Group 1, Chittagong March 27, 2014

Mendis - bird of prey or sitting duck?

Batsmen have often struggled to figure out Ajantha Mendis' bowling, but now it is time for Sri Lanka to figure out whether the spinner should be persisted with

Meet Ajantha Mendis, the wizard. He puts rabbits in his hat and yanks out dismissals. Carrom balls peg off stumps back. Two-finger googlies sneak between bat and pad. Legbreaks that take the outside edge, and offies trap batsmen off the crease. You can't come forward to him, because what if you've misread the ball? You can't just wait on the back foot, because he's quick off the pitch and the margin for error is small. His average - 14.42 - is the best for any bowler with 30 scalps or more.

Then meet Ajantha Mendis, disaster. When he sends down long hops and full tosses no one travels faster. If he has one bad over, he rarely reins it back. He holds a clutch of records, but when he concedes as many in an over as any Sri Lanka bowler before, his numbers seem hollow.

Perhaps he just had a bad day. He was only going at nine an over before Alex Hales ransacked him for 25. But it all seemed so pre-destined. With two Lasith Malinga overs stashed away for the final five, Mendis' last over was the pivot. Hales took a running leap onto his side of the see-saw and slippery-handed Sri Lanka went flying off the other end.

Few bowlers will have inspired so many team sessions hunched over the analysts' screen - batsmen looking on in a state of intrigue and befuddlement, until suddenly one of them jumps from his seat, yelling "eureka". Slowed down in high definition, all sorcery will seem little more than sleight of hand. In Tests, Mendis was dismantled and an unearthly bowling average hurtled down through the atmosphere.

That he remains effective in T20s says plenty about the format. A split second of batting hesitation cedes swathes of ground to the bowler, and Mendis can twist his hand in so many different ways, he still induces the flash of confusion that earns him his wickets

It has been difficult at times to determine what ails him when the bowler with magic fingers, suddenly appears to have grown hooves at the end of his arms. But clear patterns had also emerged, long before this World T20 campaign. Sri Lanka missed the flashing neon signs that a meltdown was imminent.

For one, Mendis is a form bowler, and one wayward outing often snowballs into several. In the past two weeks, he has been expensive against West Indies, South Africa and England. Perhaps the team's leadership had been misled by his three wickets against Netherlands, but given the seamers had already annihilated the top order before Mendis was tossed the ball in that match, that error is like falling for the "I've got your nose" trick.

More than that: there was dew. Plenty of it, since before the match began. On a clear night, following a hot day, Sri Lanka must have known the ground would be wet. It was so sodden, they rifled through five balls in their 20 overs in the field. That Mendis' grip is among the most delicate in the world is well known. That he fluffs his lines and lengths when given a soggy ball has been previously observed. When there is modest turn, as has been the case in Chittagong so far, he is vulnerable twice over, because he rarely gets the ball to spit, even in dustbowls.

"Mendis is a wicket-taker, so my expectation as a captain was that he would take wickets," Sri Lanka captain Dinesh Chandimal said, about bringing Mendis back for the over that went for 25. "When we bowled him for that last over, we needed a wicket. Unfortunately that didn't happen. Any bowler can bowl poorly and go for runs. Mendis tried to send down good overs, but unfortunately he couldn't do that in the last over. As a team we accept that. We didn't bowl well, and that's why we lost."

If Sri Lanka's spin-stocks had been threadbare, persevering so long with Mendis might be forgivable. But Rangana Herath, one of the world's most dependable spinners, warms their dugout. Mendis bags heavier hauls when he is soaring, but most sides would see Herath's economy rate of less than six and think Sri Lanka mad for keeping him out. Chandimal suggested the XI might change for the New Zealand match, and Mendis' perch is the wobbliest.

International batsmen have sunk considerable time, thought and effort into cracking the Mendis code; into knowing what is about to arrive before the ball hits the pitch. A bird of prey on some days, a sitting duck on others, Sri Lanka would do well to read Mendis better than they have in this tournament.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. He tweets here