Not a total loss for New Zealand
The conservative batting strategy should get a longer trial
New Zealand made two competitive scores in three attempts, against a good attack in tough conditions. Considering their recent results, that is not a poor return, and that mindset needs to stay for now. With the two new balls that keep swinging around for longer, yet stay hard and hittable through to the end of the innings, and the new rule that rewards aggression through the middle overs, New Zealand may have struck upon a batting strategy that others may seek to emulate, particularly on pitches that offer something for the new-ball bowlers. BJ Watling has illustrated the benefits of this approach this series, and he should retain his place in the top three when Martin Guptill returns. This may mean that Rob Nicol loses his place, or that Brendon McCullum moves to the lower middle order, displacing either Andrew Ellis or James Franklin, but either way, New Zealand should not jettison a possible fix to their batting woes.
Adam Milne should be selected more regularly - but perhaps without becoming a regular
Any team with a 20-year-old capable of bowling at 150 kph needs to invest in him, but Adam Milne may not yet be ready to become part of New Zealand's regular XI. He has a tendency to be wayward and often bowls too short, and time in domestic cricket may help him hone his game away from the pressures of international cricket. However, Milne would also benefit from testing himself against international opposition from time to time, and will learn lessons there that the New Zealand domestic scene cannot teach him. Bowling coach Shane Bond, who operated at a similar speed, had a similar build and a near identical action, and will also have plenty to add when Milne is with the team. New Zealand's selectors may need to pick and choose which tours Milne plays in for now.
Kane Williamson's role in the batting order should be clearly defined in limited-overs cricket
Throughout the World Twenty20 and at times in this series, Kane Williamson has been pushed down the order when the team has been after quick runs. There is a strong argument for Williamson being left out of the limited-overs sides altogether, not because he is unfit for them, but because at this stage of his career, he should focus solely on his Test game where his success is critical to the team's future. If the selectors insist on playing him in ODIs, however, he must be given a concrete role in the batting order. It is not fair to ask him to bat at No. 4 in one match and No. 8 not long after, and they are unlikely to get consistent contributions from him if they continue to treat him that way.
The new ball pair remains effective
Sri Lanka's pacemen, and Lasith Malinga in particular, have not had the most consistent year in ODIs, but against New Zealand, both he and Nuwan Kulasekara were menacing with the new ball. Malinga regularly beat batsmen outside off stump with movement, while Kulasekara's away-seamer - a delivery he has only recently developed, matured fully this series. There were few loose deliveries from either bowler, and they created chances at every stage of the innings.
Sri Lanka is still reliant on its experienced batsmen
Angelo Mathews made a sparkling 50 in the third ODI, albeit against bowling hampered by a wet ball, but Sri Lanka's youngsters have not yet blossomed in the top order. Lahiru Thirimanne was given two chances to impress at No. 3, but seemed unsure of how to balance aggression and defence. And although Dinesh Chandimal made 43 in the fourth ODI, he did so only after a nervy start in which he played and missed numerous times. They were given difficult conditions in which to impress, but their technical shortcomings appeared starker when their seniors handled the swinging ball with much more poise.
Jeevan Mendis is a capable second spinner
Mahela Jayawardene has been outspoken in his criticism of the new rule allowing only four men outside the circle. He had also outlined his case for why the new conditions will force teams to pick no more than one specialist slow bowler in their XI. Sri Lanka, however, have been served well by their spinning allrounder in this series, who finished joint highest wicket-taker. Jeevan Mendis' short spell in the fourth ODI secured the series for Sri Lanka. He bowled aggressively throughout the series, despite the new rules that encourage bowling quicker through the air. He is yet to find consistency in his batting, but he is doing enough with the ball and in the field to embed himself in Sri Lanka's XI.
Andrew Fernando is ESPNcricinfo's correspondent in Sri Lanka