However, the drama unfolded when Dananjaya (3-62) removed Lewis, Chris Gayle (0) and Nicholas Pooran (0) in quick succession in the fourth over to claim his hat-trick.
Pollard responded almost immediately, arriving at the crease to punish Dananjaya with six massive sixes in the sixth over, en route to an 11-ball 38 which helped West Indies regain their balance.
Even more drama erupted in the next over when Pollard was one of two wickets to fall off consecutive deliveries to leave leg-spinner Hasaranga de Silva (3-12) on a hat-trick, and West Indies stuttering again on 101 for six.
That was not the end of the tumult either as Jason Holder (29 not out) was then dropped in the deep on nine off Dananjaya and Dwayne Bravo (four not out) missed by the bowler a couple deliveries later, before West Indies gathered themselves to win comfortably in the end.
“It was a bizarre game,” a relieved Pollard said afterwards.
Debutant 22-year-old Pathum Nissanka had earlier top-scored with 39 while opener Niroshan Dickwella got 33 but Sri Lanka found themselves restricted to 131 for nine off their 20 overs.
They were well placed at one stage at 71 for one in the 10th over but then lost eight wickets for 60 runs at the back end, to fall away badly.
Sent in, they lost Danushka Gunathilaka for four in the third over to a diving catch at short mid-wicket by Pollard to give debutant off-spinner Kevin Sinclair his first international wicket but Nissanka and Dickwell put on 50 for the second wicket to repair the damage.
Nissanka faced 34 balls and struck four fours and a six while the left-handed Dickwella punched three fours and a six off 29 deliveries.
Fast bowler Holder broke the stand when Dickwella tried to sweep a low full toss and had his stumps rattled off the final ball of the 10th over and Nissanka followed in the 13th, missing a charge at left-arm spinner Fabian Allen and leaving Pooran to complete a straightforward stumping.
A rain break did little to improve Sri Lanka’s fortunes as left-arm seamer Obed McCoy (2-25) snatched two wickets following the resumption to help accelerate the innings decline.
In reply, Lewis lashed three sixes in the opening over from captain Angelo Mathews’ gentle medium pace and added later two fours in a whirlwind 10-ball knock while Simmons hit three fours and two sixes off 15 balls, in a rapid start for West Indies.
And the home side appeared set for an easy victory before Lewis holed out to long off and veteran left-hander Gayle then got one that spun past an uncertain defensive prod to hit the front and back pad, for what should have been a straightforward LBW decision but was only gained through DRS.
When Pooran nicked the next ball behind, an elated Dananjaya had claimed the 14th hat-trick in T20 Internationals.
Simmons missed a sweep at Hasaranga and was lbw at the end of the fifth at 62 for four but Pollard eased tensions with his stunning achievement in the next over.
He was looking to push on when he failed to navigate a Hasaranga googly and was lbw and Allen followed next ball, also lbw playing down the wrong line to another googly.