The Volts play the Auckland Aces at Eden Park tonight, with the sides fresh off a tight twenty/20 match just under a week ago.
In a quirk of the draw, they face off again for the second time in five days, with Otago having won the previous encounter in Queenstown by 13 runs.
Johnson said the Volts were performing well but were not getting carried away after securing a fourth win in a row by beating Auckland.
''I think we are doing a little bit better than all right. You can get on a roll in these sort of games but I don't think you can ever get ahead of yourself and look too far down the track,'' Johnson said.
''We just have to make sure we play well and then the results will take care of themselves. We showed in Queenstown when we lost a few early but then Tendo [Ryan ten Doeschate] and Neesham [Jimmy Neesham] got in and put on a 100-run partnership.
''It is that sort of game where you can be bowled out really quickly for nothing or you can go out there and get 180-plus.''
Playing on Eden Park offered something different, Johnson said, with the dimensions of the ground giving challenges to bowlers and the setting of fields.
''I would think 180 is the minimum you would have to get on that ground. But conditions come into it and it is also a drop-in pitch which can make a difference.''
The angles of the pitch mean it can be a difficult ground for bowlers should they be slightly wide in their delivery. It is not a huge distance for straight hits, either.
Otago will be without Black Caps all-rounder Nathan McCullum, who has a hamstring injury. Sam Wells and Iain Robertson come into a squad of 13.
Johnson said it was always exciting to play under lights at a big ground such as Eden Park and the team was looking forward to getting involved.
Auckland has retained the same 13 players which lost in Queenstown and it is shaping up to be an important match for the defending champion.
The Aces have won only two games from five and need to stay handy to be in with a chance of making the finals. The likes of Colin Munro and Colin de Grandhomme are due to make an impact, while English import Phil Mustard put together an impressive knock at the last home game.
Otago has won its games through a combination of good batting and bowling. If one has not fired, the other has come to the fore.
Import ten Doeschate again looms as the key man for Otago, while young bowlers Jacob Duffy and James Fuller will again have to step up.
Whatever happens tonight, the Otago players will not have a lot of time to dwell on the result. They will get on a plane early tomorrow morning and may have an optional practice tomorrow afternoon before taking on the Central Stags at the University Oval on Sunday afternoon.
HRV Cup
Auckland, tonight, 7pm
Otago: Aaron Redmond, Hamish Rutherford, Neil Broom, Ryan ten Doeschate, Michael Bracewell, Sam Wells, Jimmy Neesham, Iain Robertson, Ian Butler, James Fuller, Derek de Boorder (captain), Jacob Duffy, Nick Beard.
Auckland: Gareth Hopkins (captain), Andre Adams, Michael Bates, Craig Cachopa, Colin de Grandhomme, Donovan Grobbelaar, Anaru Kitchen, Kyle Mills, Phil Mustard, Matt Quinn, Bhupinder Singh, Lou Vincent, Reece Young.
Points: Northern Districts (played seven) 20, Otago (five) 16, Wellington (seven) 16, Auckland (five) 8, Canterbury (six) 8, Central Districts (six) 4.
