Mendis was unbeaten on 141 and Mathews 120 not out at stumps after a 274-run stand that, along with the weather, allowed Sri Lanka to salvage a draw.
New Zealand will view the draw as a missed opportunity after they took control of the Test with a mammoth 578 in the first innings, anchored by Tom Latham’s unbeaten 264.
This is a Test between a team ranked No. 6 that has just been walloped 3-0 at home, and a No. 4 side that has just returned from a 2-1 triumph overseas. That the series takes place in the the higher-ranked outfit's own conditions further underlines who the favourites here are.
There is stability for New Zealand. There is a highly-rated captain who has been in the job for almost three years. There is a well-heeled and confident attack. A solid top order. A reliable backroom. They've travelled across continents since their last Test, and arrived at the Basin Reserve where, by Kane Williamson's own estimation, the conditions they will encounter are the "polar opposite" to those last week in Abu Dhabi, and yet, they have made only one change to the XI, switching out the offspinner William Somerville for the fast bowler Neil Wagner. You get the feeling there is a plan at work here. That they are building to something. Perhaps something special.
The visitors, meanwhile, are scrambling. The poor returns against England first cost the selectors their jobs. The fielding coach and batting coach have also since been told they will be replaced. In truth, Sri Lanka's Test record over the past 18 months is not all that awful - they've won series against South Africa, Pakistan and Bangladesh, and drawn a series in the West Indies. But being whitewashed at home by England last month has stung. The whole system suddenly seems a little shaken. Now, they are in a country where they last won a Test 12 years ago, and where they have been more-or-less thumped in four matches this decade.
There is, however, a glimmer of hope for Sri Lanka, and that is their young, exciting seam-bowling battery. The last time Sri Lanka fielded three frontline quicks in a match, as they are almost certain to do in Wellington, they blasted out West Indies for 93 in Barbados, overturning a first-innings deficit, and setting up a win. Lahiru Kumara, the quickest in Sri Lanka's ranks, took 17 wickets at less than 20 apiece in that series. Kasun Rajitha seamed the ball viciously in his first two matches. Dushmantha Chameera, meanwhile, has already had one good tour of New Zealand, back in 2015-16.
But so infrequently do Sri Lanka play on seam-friendly tracks, it is difficult to gauge how good these bowlers actually are. Will they really be menacing and dynamic? Or will Williamson and co. wear them down, then exploit their inexperience? Sri Lanka have to hope they have some special young talents in their side. Form and proven quality are decidedly with New Zealand. All that remains to the visitors is surprise.
Form guide
Sri Lanka LLLWW (last five Tests, most recent first)
New Zealand WLWDW
Henry Nicholls shows off his leg-side game Getty Images
In the spotlight
Henry Nicholls had skated by on a modest average for the first 16 Tests of his career, but 2018 might just be the making of the man. He made 145 not out against England, in Auckland, to begin the year, but it was in the UAE last month that he truly blossomed, making scores of 55 and 77 before his outstanding match-turning second-innings 126 not out in the company of Williamson, in Abu Dhabi. A good series at home to follow an excellent one overseas would help cement a burgeoning reputation as a reliable middle-order batsman.
Of Sri Lanka's batsmen, only opener Dimuth Karunaratne has a hundred in New Zealand - his 152 in Christchurch at the end of 2014. He also comes into the series with a little batting form, having made 256 runs at 42.66 against England, after having dominated the home series against South Africa earlier in the year. Now the team's vice-captain, Sri Lanka will look to him for some serious stability against the new ball, because it is a shaky middle order that he is protecting.
Team news
New Zealand have named their XI. They will go with the tried-and-tested pace trio of Trent Boult, Tim Southee and Neil Wagner, with Ajaz Patel as the sole specialist spinner.
New Zealand: 1 Jeet Raval, 2 Tom Latham, 3 Kane Williamson (capt), 4 Ross Taylor, 5 Henry Nicholls, 6 BJ Watling (wk), 7 Colin de Grandhomme, 8 Tim Southee, 9 Neil Wagner, 10 Ajaz Patel, 11 Trent Boult
Sri Lanka's line-up is a little tougher to predict. Danushka Gunathilaka probably played himself into an opening spot with a second-innings 83 in the practice match. Suranga Lakmal and Lahiru Kumara are likely to be the first seamers chosen, with Kasun Rajitha, Nuwan Pradeep and Dushmantha Chameera fighting for the third seamer's spot.
Sri Lanka (possible): 1 Dimuth Karunaratne, 2 Danushka Gunathilaka , 3 Dhananjaya de Silva, 4 Kusal Mendis, 5 Dinesh Chandimal (capt), 6 Angelo Mathews, 7 Niroshan Dickwella (wk), 8 Dilruwan Perera, 9 Suranga Lakmal, 10 Kasun Rajitha, 11 Lahiru Kumara
Pitch and conditions
The pitch was barely distinguishable from the outfield on the eve of the match, but the general trend for Basin Reserve surfaces is that they dry out after day two and become very good for batting on days three and four.
Stats and trivia
Kane Williamson averages 91.88 after 12 innings against Sri Lanka. This is his highest average against any Test nation. After his ton in the second innings in Abu Dhabi, he also only needs one more century to become the first New Zealand batsman to make 20 tons.
Sri Lanka have lost each of their last five Tests against New Zealand - four of them in New Zealand, and one in Sri Lanka.
Sri Lanka's most recent win in New Zealand came at the Basin Reserve, back in 2006.
New Zealand will become the No. 2 ranked team in the world if they win the series 2-0.
Quotes
"You do as much homework as you can, but there's some bowlers some guys haven't seen. That's the beauty of international cricket, in that you do see other countries' depth. We know that by all accounts there is a really talented fast bowling group in the Sri Lankan side. I'm sure they're really excited to get into the Test tomorrow. ."
New Zealand captain Kane Williamson on Sri Lanka's pace battery
"Straight after the series finished against Englnad we had three or four practice sessions. We knew that when we came to New Zealand we'd definitely get grassy pitches. We kept grass on our pitches and had really good preparation."
Sri Lanka captain Dinesh Chandimal
Match Coverage
All Match News
Two guys put their hands up and didn't give us an opportunity for a day - Williamson
Kane Williamson's team tried everything, but Sri Lanka's batsmen were just too good
Kusal Mendis the dasher turns into Thilan Samaraweera clone
Usually an unrepentant strokemaker, Sri Lanka's No. 4 overturned his batting style to block his way to an outstanding match-saving hundred
Kusal Mendis eyes double-ton as mentor Samaraweera's send-off gift
Sri Lanka batting coach Thilan Samaraweera will exit the role at the end of this series, and Kusal Mendis is keen on fulfilling his wish
Rain completes Mathews and Mendis' epic rescue
The pair batted all of the fourth day and 12 overs on the fifth before weather intervened to give Sri Lanka a draw that didn't look possible at 13 for 3
When I saw Angie get hit, I thought there's no way I'm getting out - Mendis
Sometimes guilty of playing attractive but insubstantial innings, Mendis partnered a steadfast Mathews for the entirety of day four in Wellington
