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Their struggles mean New Zealand's middle order has been left to face balls whose gilded lettering has barely been removed.
Before the second test against South Africa, the pair had opened together 10 times since that first Indian test in Hyderabad. Their highest partnership in that period was 32 runs (the second innings vs Sri Lanka in Colombo) and the longest time spent at the wicket 14.3 overs (compiling 26 vs India in Hyderabad).
To make matters worse, the highest partnership and longest time at the crease in the first innings of tests has been 29 runs in 5.1 overs (vs Sri Lanka in Galle). On four occasions, including two in the Cape Town test, they have not lasted two overs.
In 19 opening stands since Guptill joined the team in 2009, the pair have produced two century partnerships (vs Pakistan in 2011 and Zimbabwe in 2012) but have otherwise not exceeded 44. They also produced a partnership of 123 for the second wicket in the Antigua test loss to the West Indies in July.
As the batsmen underwent their short-range artillery training after "that 45 innings", there appeared limited options for change. Both players can make a strong case to remain in the test XI given New Zealand's lack of depth.
New captain McCullum remains one of the touring party's best batsmen, while Guptill won a rare Twenty20 international this tour with a century against South Africa. While T20 can't be compared to the test game, it shows Guptill has not lost his talent.
Pushing either player down the order seems futile, as do the opening alternatives. No new Mark Richardson or Glenn Turner is demanding selection.
The only solution appears to be for McCullum and Guptill to galvanise their techniques and banish any mental fragility; not easy concepts to master when Dale Steyn, Vernon Philander and Morne Morkel have been bearing down, albeit with Philander missing the second test.
Emerging from their current partnership trough could be one of the toughest things Guptill and McCullum address in their careers.
McCullum's main test batting problem appears to be balancing aggression with patience. It was a concept addressed by former New Zealand captain Martin Crowe in his recent open letter to Cricinfo before the second test against Sri Lanka. Crowe recommended McCullum drop down the order to five.
Given that's unlikely to happen, he said the skipper needed to build an "impregnable defence" to keep out wicket-taking balls. Crowe pointed out once that happens, "the rest of the balls you face are run-scoring opportunities". He said all today's prolific run-scorers have "trained their mind to sense once the ball leaves the hand whether it is a wicket-taking ball or boundary ball".
Those thoughts are borne out in McCullum's recent record. He is capable of getting to 50, having done so six times as an opener in 27 test innings - including four in the first turn at bat - but struggles to go on. McCullum has scored one century opening for New Zealand (225 at Hyderabad in November 2010). His other five have come batting at No 7. His average of 37.68 as an opener continues to drop towards his overall test average of 35.52.
Former test opener-turned-media pundit Craig Cumming has identified a problem with Guptill's straight front leg when he plays forward. Cumming said it tends to be a limited-overs habit - born of trying to make runs off every ball. More tension at the point of impact combined with a seaming pitch means the ball travels further when it collects the edge and brings the slip cordon into play.
Guptill needs remedial work to boost an ailing test average of 30.83 (26.62 as an opener).
He averages 245 against Bangladesh (from one test), 53.33 against Zimbabwe and 69.25 against the West Indies but less than 20 against South Africa, Australia and Sri Lanka.
Guptill suffered criticism by some Twitter followers during the week after noting he was embarking on a great white shark diving excursion, despite making one run over 11 minutes and 12 deliveries in the opening test.
However, even cricket sides who get out for 45 need to take their minds off work. The team practised on what would have been days four and five in Cape Town. Guptill now needs to prove those efforts to balance work and play have not been in vain.
- Andrew Alderson