The win means Afghanistan are through to the Super Four stage of the tournament, along with Bangladesh.
It was in the field and with the bat that Sri Lanka dug their own grave, as had been the case on Saturday against Bangladesh. Another catch was dropped off the opposition's top-scorer, while run-out chances were missed, and ground fielding continued to be slopy. Then, with bat in hand, Sri Lanka never seemed to have the measure of the target. Kusal Mendis was out second ball, trapped lbw by a drifting Mujeeb Ur Rahman delivery. And although at times Sri Lanka threatened to build partnerships, they somehow found ways to self-destruct. There were two run-outs in the innings, several strange and fatal shot choices, and an overall theme of inadequacy and mayhem to the innings.
As expected, Afghanistan's trio of match-turning spinners wreaked havoc, but right-arm seamer Gulbadin Naib also shared in the fun. Naib, Rashid Khan, Mujeeb and Mohammad Nabi took two wickets apiece, with all four of these bowlers conceding comfortably less than four an over. So comprehensive was this victory, that you would never guess Sri Lanka were the team who have won this tournament five times, and the opposition were the upstarts. Afghanistan seemed in control of this game from the very outset, when they put on 57 for the first wicket. Their only wobble was in the final 10 overs of their innings, when they managed only 66 runs, and lost seven wickets.
Twice, Sri Lanka suggested they would set about calmly knocking off this score, only for disaster to strike. Tharanga and Dhananjaya de Silva put on 54 for the second wicket, without being too sorely tested by the oppostion's bowlers, until de Silva attempted a very poorly second run despite the strong protestations of his partner, and got himself run-out in a scenario in which both batsmen ended up at the same end. Later, after a second running mix-up - for which Angelo Mathews was largely to blame - Sri Lanka were tottering at 108 for 5. Mathews and Thisara Perera seemed to dig in and start a rescue, only for Mathews to hole out to long-on attempting to hit a much-needed boundary.
It is true that Sri Lanka's batsmen often attempted poorly-conceived strokes - Kusal Perera was a prime example, attempting a pre-meditated slog sweep off Rashid's very first over, which ended with his off stump pegged back. But they were usually bullied into a panic by a disciplined and relentless Afghanistan attack, which gave away very few loose deliveries, while their fielders backed the bowlers up in clinical fashion. If there is some kind of modest defence of the Sri Lanka batsmen, it is that they generally tried to pierce the field before losing their wicket trying to hit over it. In the end, Sri Lanka didn't even get close - the last five wickets falling for 15 runs - with Rashid landing the final blow.
In their own innings, Afghanistan had been steady, right up until the 42nd over. Mohammad Shahzad hit 34 - occasionally flirting with disaster, without embracing it like several Sri Lanka batsman would do later in the evening. His opening partner Ihsanullah hit 45 off 65 balls, before eventually being dismissed lbw by Akila Dananjaya, just like Shahzad.
Although neither opener reached a half-century, they had left Afghanistan in a decent position - at 107 for 2 in the 25th over, at Ishanullah's departure. Shah took over after that, and his was mostly a controlled innings - the likes of which he has played many times over the last 18 months, as Afghanistan's most consistent batsman. Though first scoring shot was streaky - an outside edge off Dananjaya evading first slip - he settled nicely thereafter, finding singles and twos into a now-spread field. Afghanistan's first three dismissals were all lbws, but Shah ensured he blocked out the majority of the straight deliveries the spinners delivered to him.
He was so conservative, in fact, that he didn't hit his first boundary until his 44th ball, crashing Shehan Jayasuriya's offspin through the covers after backing away and making room. He was more adventurous later in his innings, reaching fifty off the 63rd ball he faced with a four over mid-on, and then venturing a couple more boundaries square, on either side of the pitch. Attempting to raise the tempo in the 42nd over, he could only hit a slower ball from Dushmantha Chameera as far as long on, where Thisara completed an overhead catch.
Sri Lanka's bowlers would regroup through the last nine overs, with Thisara proving penetrative in particular, completing his first five-wicket haul since 2012, relying mostly on yorkers for those wickets. Three of Thisara's dismissals, however, came in the final over of the innings and so as five-fors go, this one did not have a substantial effect on the opposition's score.
In any case, Sri Lanka batted so poorly against a spirited Afghanistan attack, there was perhaps little their bowlers could have done to save them.