'Poor catching, batting cost us, not complacency' - Herath
Rangana Herath, the Sri Lanka captain, said he was confident of defending 191 in the fourth innings, although they would have liked more runs to work with. Herath has been the central figure in each of Sri Lanka's five most recent home victories, when they have bowled out visiting sides for 171 (West Indies), 161, 183 and 160 (Australia), as well as dismissing Bangladesh for 197 in Galle.
However, though Herath struck early in Bangladesh's final-day chase at P Sara, removing Soumya Sarkar and Imrul Kayes off consecutive deliveries, he couldn't sufficiently quell Tamim Iqbal or the Bangladesh middle order.
"I really thought that we could defend it, because we have played games with India and Pakistan and defended low scores," Herath said. "We also had three spinners. When we got two early wickets, I felt the same way, but after lunch they were in an attacking mood and scored some quick runs. That's where the match slipped from us in the fourth innings."
Herath also pinpointed Sri Lanka's catching at the end of day two and their collapse on the fourth afternoon as definitive passages of play. Of particular consequence was the dropped catch off Shakib - he was spilled by Upul Tharanga at deep square leg on 11 - with Sri Lanka spurning the chance to have Bangladesh 210 for 6 after the hosts had hit 338. Bangladesh would eventually go on to establish a first-innings lead of 129.
"I thought we made too many mistakes while fielding and batting," Herath said. "We dropped a couple of crucial catches and that was the main reason for us to lose the match. Shakib's catch was especially bad because he went on to a century. With a team this competitive, we can't let the little mistakes like that that come into our game."
Though Sri Lanka began the third innings well, pulling into the lead with nine wickets remaining, they had a horror session after lunch on the fourth day. Five top order batsmen were out in the space of 15 overs, to Mustafizur Rahman and Shakib.
"If you take the second innings we were batting well. After Upul Tharanga got out, Dimuth Karunaratne and Kusal Mendis were going great. Then Kusal got out and suddenly we lost four more wickets for 40-odd runs. That was the key and that's what we should have prevented. That was the start of our downfall."
Herath said the loss was "one of" the worst defeats of his career, but was adamant that at no stage did Sri Lanka underestimate Bangladesh. Sri Lanka are 31 points clear of Bangladesh on the Test rankings, but are only two places ahead - seventh, where Bangladesh are ninth.
"Before the series started I said that this was a challenging series as both teams were equally matched. We had a good chance in Galle as we got close to 500 runs, and we capitalised. Here we couldn't do the same.
"Bangladesh have certainly improved a lot. Earlier when they got partnerships going, we would put pressure on them, and they wouldn't be able to handle that. This team tries to stay in the game a lot more, and now they counter our plans. They have been very clever."
Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando