A “miracle ball” from the recalled Neil Wagner set New Zealand up for a 122-run win in the first Test on Monday as Sri Lanka folded with the loss of seven wickets on the final day.

New Zealand had set the Sri Lankans a formidable 405-run target but with sufficient time to get there on a non-threatening University Oval wicket.

The Sri Lanka batsmen, however, failed to show the necessary patience and were all out for 282 midway though the final day.

Resistance crumbled after Wagner, back in the side after a year out of Test cricket, captured the crucial scalp of Angelo Mathews, who had put on 56 with Dinesh Chandimal for the fourth wicket.

After being peppered by short deliveries targeting the rib cage, Mathews, on 25, was taken by surprise by a full-length delivery which rattled into his stumps.

His dismissal upset the rhythm of top-scorer Chandimal (58) who only lasted another 17 balls before he was beaten by Mitchell Santner.

“Neil Wagner really stepped up for us,” captain Brendon McCullum said of the left-arm seamer playing his 18th Test.

“Once he got that breakthrough, got Angelo out, then we certainly relaxed the shoulders after that and were able to push home the advantage.

“It was beautifully set up. Wags decided that at some stage he was going to bowl the miracle ball, try and hit the base of leg stump and in the end it split his defence.”

Sri Lankan captain Mathews, who acknowledged being caught in a Wagner “trap”, described the match as a learning experience for his young side.

“Most of the batters were solid in technique. It’s just the mindset that we’ve got to shift around a little bit,” he said.

“We’ve got so many inexperienced guys at the moment, it’ll take a bit of time to get going.”

The comprehensive victory gave New Zealand their fourth consecutive win over Sri Lanka in the past three years. (AFP)