A more assertive positioning of National Australia Bank's domestic business might be taking shape under new CEO Andrew Thorburn, if management changes unveiled on Friday are any guide.Joseph Healy, Lisa Gray and Bruce Munro, three of the generals of the Clyne era, are leaving NAB, Thorburn disclosed on Friday.Betrayed by a falling market share and few lasting gains from the "break up" era, Thorburn, no doubt backed by his board, is looking for change.Insiders are replacing the three, in a show of confidence in internal training.In total there are four additions to the NAB group executive.Angela Mentis, previously executive general manager of nabBusiness in business banking, replaces Joseph Healy.Antony Cahill will take up a newly defined role of group executive for product and markets.  Cahill was previously executive general manager of lending and deposits.David Gall will become chief risk officer, replacing Bruce Munro. Gall was previously executive general manager of banking and wealth solutions.Renee Roberts takes over as group executive for enterprise services and transformation. Roberts was previously chief risk officer of Bank of New Zealand. She replaces Lisa Gray.Healy and Gray have "both decided now is the appropriate time to leave NAB," in the euphemism of the NAB announcement, while Munro is said to be retiring. Both Healy and Gray were the line executives most frequently wheeled out over recent years to spruik the bank's strategy and positioning. Both were central figures - in the case of Gray, earlier, running retail banking - in shaping the NAB business of today.NAB' share of business lending was 22.8 per cent in June 2014. Eighteen months earlier its market share was 25 per cent.In personal banking, the "break up" and "fair value" strategies delivered some improvement in market share but the bank failed to maintain momentum, stuck at 16.6 per cent on mortgages.NAB has lost market share in credit cards and cannot be content with its private banking and wealth management arms.Third party lending, through the division formerly known as Homeside, is the real bright spark of NAB and is getting extra investment.The Oracle IT transformation project is one consuming project where Thorburn will have to show value.And finally find a way for NAB to break out.