Chasing Sri Lanka’s 280/9 on a good batting pitch at the SSC, Bangladesh failed to score big and were eventually bowled out for 210 in 44.3 overs.
The Tigers made a shaky start as left-handed opening batsman Tamim Iqbal (four).
was caught and bowled by pacer Nuwan Kulasekara.
Prior to Tamim's dismissal, one of his edges flew past wicket-keeper Dinesh Chandimal but the southpaw was unable to capitalise on the opportunity.
No 3 batsman Sabbir Rahman (nought) also departed soon after while chasing a wide delivery from Kulasekara in the third over.
The situation turned worse for Bangladesh in the very next over when seamer Suranga Lakmal trapped Mushfiqur Rahim (nought) in front.
Bangladesh were stuttering at that moment with the scoreboard reading 11/3 in 3.3 overs.
However, the other opener Soumya Sarkar and all-rounder Shakib al Hasan stemmed the fall of wickets, forming a 77-run partnership for the fourth wicket.
But Soumya got out in the 16th over after scoring 38 and from thereon in, Bangladesh lost wickets at regular intervals. Shakib scored a composed half-century but he too was dismissed for 54 in the 24th over.
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Shakib al Hasan's composed half-century proved to be nothing but a consolation in the context of the game AFP
Youngster Mehedi Hasan Miraz and No 10 Taskin Ahmed offered some resistance in the latter part of the innings. Miraz (51) scored his maiden ODI half-century with half a dozen boundaries. Taskin (14) was the last batsman out for Bangladesh.
Kulasekara was the most successful bowler for the home side picking up four wickets conceding 37 runs.
Earlier, limited-over skipper Mashrafe bin Mortaza won the toss and elected to field first.
The Lankan openers Upul Tharanga and Danushka Gunathilaka scripted a brilliant stand scoring some quick runs. After 10 overs, they were 76 without loss and cruising towards a big total.
Miraz initiated the first breakthrough in the 11th over when Gunathilaka was caught by Mahmudullah after scoring 34 off 38 balls.
Taskin then got an important scalp by dismissing the well-set Tharanga (35) in the 14th over. It was a magnificent delivery by Taskin and the makeshift Lankan captain was clearly beaten for pace. Tharanga's run-a-ball knock featured five fours and a six.
Kusal Mendis and Chandimal then added 49 runs for the third wicket. Chandimal however, was caught short of the crease in bizarre fashion. The stumper-batsman was well inside the line but his feet and bat were off the ground when Mushfiq dislodged the bails from a Taskin throw from deep point.
But the in-form Mendis, who scored a century in the second ODI, carried on his good form and registered a fifty in the 34th over.
Bangladesh then bagged regular wickets and were able to put a lid on Sri Lanka's run rate in the middle period of the innings. At one stage, they were 216/6 in 43.3 overs.
All-rounder Thisara Perera then took over, lifting his side towards a competitive total courtesy his brisk half-century.
Mashrafe picked up three wickets for Bangladesh conceding 65 runs while pacer Mustafizur Rahman took two for 55 runs.
210 in 44.3 overs (Shakib 54, Miraz 51) lost to Sri Lanka
280/9 (Mendis 54, Mashrafe 3/65) by 70 runs