New Zealand top group one with five points and a considerable advantage in net run rate. Their position could be even stronger had the weather played its part against Afghanistan, but any damage from that no result was lessened by Australia and England having their heavyweight clash rained out.
England will be the Black Caps' next opponents on Tuesday, but even defeat in that match will likely matter little as long as they then avoid an upset against Ireland in their final group match.
Much is owed to Phillips for that comfortable perch. Hit ton was the first scored by a batsman outside of the top three in a T20 World Cup, while he became the second Kiwi after Brendon McCullum to reach three figures at the tournament.
He and New Zealand received a significant slice of fortune early in his innings, when Pathum Nissanka spilled a simple catch at long on with Phillips on 12. From there, though, he seized control of the innings and the match, battling cramp as much as he did the Sri Lankan bowlers.
Such a commanding knock was sorely needed after the Black Caps' early stumbles.
Neither Finn Allen nor Devon Conway was able to back up a brilliant performance against Australia, both dismissed for one as Sri Lanka opened with spin and found immediate reward. Once Kane Williamson was nicked out for eight, he could have been reconsidering his call to bat first.
That, however, was when Phillips took charge. He didn't immediately find scoring easy on a tricky deck, consolidating with Daryl Mitchell (22 off 24) in a partnership that initially limited risks but did nothing to hasten the run rate.
But after being given a life, Phillips lived a full one, hitting the first six of the innings over fine leg in the 10th over before launching with 18 runs from the 14th. The end of his 84-run stand with Mitchell did nothing to lessen his aggression, with the returning allrounder very much the junior partner.
Phillips' strength was his most prominent attribute, giving himself plenty of room and muscling the ball to the fence with some unconventional shotmaking. Having sounded audibly frustrated when playing and missing on a couple of occasions, he saved his biggest roar for the pull that brought up his second T20I century.
The Auckland batsman celebrated the milestone in exuberant fashion, and justifiably so. He hit 10 fours and six sixes during his stay, while his teammates collectively managed 14 runs in boundaries. Phillips struck at 162.5 while the other eight Black Caps to bat needed 59 balls to score their 53 runs.
This was close a one-man team - until, that is, it was Sri Lanka's turn to bat. With Phillips remaining in the pavilion to recover from his efforts, Boult and Tim Southee would have made for pleasant viewing from the sidelines.
Southee started with a wicket-maiden and Boult responded by snaring two scalps in the second over, dropping Sri Lanka to 5-3. Unlike earlier in the evening, there would be no saviour for the Asia Cup champions.
New Zealand's fielding was again excellent - a marked contrast to their opponents' - even with Phillips limited to a cameo before succumbing once and for all to cramp.
Boult and Southee (1-12) combined to lock down Sri Lanka for eight overs, while Mitchell Santner and Ish Sodhi shared four wickets to finish them off.
