The gap between New Zealand and South Africa appears to be growing, but Martin Guptill says his side are staying positive ahead of Saturday\'s final one-dayer in Auckland. After last night\'s crushing in Napier, the Black Caps have now lost four straight games to a punishing Proteas side, giving the hosts little to shout about heading into the three-match test series starting next Wednesday. And if a team\'s superiority only grows with the length of the game, there is unlikely to be any respite in the near future. Despite being a clear second best in the first two ODIs, Guptill said the Black Caps weren\'t about to dwell on the defeats. \"If we\'re going to be negative we\'re going to get absolutely trounced. We need to stay positive as a team and as a unit.\'\' The first two matches in the one-day series may not have been absolute trouncings but they weren\'t too far away. Both featured solid batting starts by New Zealand undone by middle-order collapses, and both saw South Africa cruise to their target with plenty of wickets and overs to spare. Napier was a particularly grisly scene, as the Blacks Caps fell from 162-2 to 230 all out in the space of 15 overs, a target South Africa needed only 38 overs to haul in. But Guptill thought that margin of victory belied the competitiveness between the sides. \"We knew they were going to be a classy outfit when they came over,\'\' he said. \"It\'s just about winning those key moments in games, which we didn\'t win last night.\'\' One of those key moments in which the hosts suffered a significant set-back last night came during the batting powerplay. Instead of accelerating the scoring and building on their solid foundation, New Zealand took just 20 runs from five overs and, in the process, lost the valuable wickets of Kane Williamson, Brendon McCullum and Jesse Ryder. McCullum\'s departure, in particular, was frustrating given the wicketkeeper-batsman was set at the crease and wasted the chance to notch a match-winning score for the second game in a row. He was out for 85, four days after falling for 56, but he was by no means the only culprit. Guptill, who made 58 opening the innings, struggled for an explanation why the Black Caps\' batsmen have failed to turn starts into big scores. \"It\'s just one of those things that comes with cricket - some days you can kick on and get a big score and some days you play a loose shot and get out.\'\' It just seems as the latter is occurring a lot more readily during the South African tour, but Guptill denied the New Zealanders were experiencing a form slump. \"It\'s definitely a disappointment, but we\'re still playing some good cricket in patches and we just need to put the good cricket in for longer periods of time.\'\' Of course, the recent woes may have something to do with the opposition, the third-best side in one-day cricket. Guptill said despite the apparent gulf in class, all was not lost. \"We showed in that first Twenty20 in Wellington we can make that step up. The last four games haven\'t really gone our way, but if we can get back into that frame of mind we had in that Twenty20 in Wellington then I think we\'re going to put up a better fight in the next few games. \"If we can get a win under the belt on Saturday it\'s going to give us a bit of momentum heading into the test match series.\'\' They\'re probably going to need it.