Morrison wasn't intending to leave his post until 2017 or 2018, but Harrison said yesterday's resignation meant it was now unclear who the new chief executive might be.
"James would be a strong candidate and Nigel would have recommended him," he said.
Those who work closely with Morrison include general counsel and company secretary Peter Treacy, group services and human resources general manager Grainne Troute, international business president Ejaaz Dean and group general manager Simon Jamieson.
Harrison said it was not clear who would become chief financial officer.
"Nigel is not talking about leaving, so there's still plenty of time to appoint a new CEO. The important thing now is to replace the CFO and then look at the CEO role."
Nachi Moghe of Morningstar expected Burrell to stay for SkyCity's $850 million Auckland and Adelaide expansion.
"It's a lot of money, this next leg of growth for the company, so this is a bit of a shock," he said.
"If it was dull and boring, I could understand him leaving. These are exciting times."
Chris Gaskin of Devon Funds regretted Burrell's departure, but said Morrison had shown an ability to attract experienced gaming management so he did not expect issues getting a new CFO of equal calibre.
Another funds manager said Burrell was the counter-balance to Morrison, "one of our more colourful corporate citizens. James pulled him back. He was good at managing him". Morrison said Burrell had ably led the finance team.
"Many milestones have been achieved during his three years with us," Morrison said.
"While we are disappointed to be losing James as our CFO, we respect his family decision to return to England at the end of June after being away from home for six years.
"He and his wife Sue have a young family and they want to be closer to their extended families."
