England's national director of improvement and efficiency, Jim Easton, admitted the NHS was now entering 'very choppy, grade five rapids' as it bids to make £15 to £20 billion in efficiency savings.
At a King's Fund event on productivity in London last week, the think tank's chief economist, Professor John Appleby, urged commissioners to concentrate on how the released resources will be used to benefit patients.
Professor Appleby said 'as the money tap is turned off', productivity in the NHS will increase. He predicted figures from the Office of National Statistics for this financial year and next would show productivity in the NHS has improved.
'The NHS will trundle on producing outputs,' he said.
'The trouble is, it is a bit like an orchestra when you take the conductor away: it will carry on playing for some time, but it will gradually go out of tune and miss a beat. After a couple of years we will potentially see problems in the NHS.'
Professor Appleby said the productivity challenge is an 'absolutely huge task' and he added that there was 'massive over-complication and confusion' about the issue.
The NHS needs to 'obsess less' about making cuts and savings and focus more on what actions will generate benefits for patients, he said.
'Saving money simply for saving money's sake is absolutely not the point,' he said.
'Yes, save money, but then actually do something valuable with that resource.'
Meanwhile, Mr Easton said PCTs across most of England have 'decent' savings plans under the Quality Improvement Productivity and Prevention programme.
He said: 'These are interesting times. It is now getting real and we are going to enter choppy, grade five rapids. The real issue is how to do it.'