"The Super Fund stake is the last accessible stake in that name. People who missed out on getting some of that stock have had to make a choice about what they were going to do next," Williams said. "There were people who were left short - and, if you believe the broker, they were many times oversubscribed for what they had. Probably the last liquidity event has occurred and people have been left with not as much stock as they would like."
The index's dip was logical given the market's strong run, Williams said, but selling in some stocks could also have been driven by people looking to fund their purchase of Z Energy.
"For lots of people, if they're wanting to buy Z, they're having to fund it from somewhere - most people would be largely or fully invested," Williams said. "For example, there's Sky City, which is performing operationally very well and has no ... reason to be down except for the fact it's a very liquid name and people can raise money to pay for participation in Z there."
SkyCity Entertainment Group dipped 1.3 per cent to $4.67, Fisher & Paykel Healthcare fell 2.1 per cent to $10.52 and Fletcher Building dropped 1.8 per cent to $8.67.
Steel & Tube was the worst performer on the index, down 5.2 per cent to $1.84.
In a statement published to the market on Wednesday, Steel & Tube said it was in talks with "multiple agencies" in New Zealand and China over pile casing that was to be used in bridges for the Huntly bypass that were sub-par.
The company said it had incorporated the impact in downgraded earnings guidance last month.
Greg Smith, head of research at Fat Prophets, said sentiment was against the company after a run of problems.
"It's fair to say sentiment is at a fairly low ebb. Management came out with an earnings downgrade last month, there are the Huntly casings all over the media, it's one thing after another for it," Smith said.
"It needs to hit the revised full-year earnings, perhaps exceed it a little bit, that could be a catalyst."
Kathmandu Holdings dropped 3.2 per cent to $1.51, A2 Milk Co fell 3.2 per cent to $1.52, and Australia & New Zealand Banking Corp declined 3.1 per cent to $26.35.
Xero was the best performer on the index, rising 3.6 per cent to $18.64. Orion Health Group rose 2.9 per cent to $5.31 and New Zealand Refining Co gained 2.4 per cent to $2.57.
Restaurant Brands New Zealand rose 0.2 per cent to $5.56. The fast-food retailer lifted first-quarter sales 8.5 per cent as the acquisition of New South Wales' biggest KFC franchise bolstered revenue in the period.
Restaurant Brands' shares have soared on the prospects of Australian earnings growth from KFC, its most successful New Zealand brand.
