Dr Evans made the comments on BBC Scotland’s Sunday Show, where she called for a “long-term plan” for the NHS workforce in addition to sustainable investment.
Asked if the ongoing NHS Scotland crisis is “in essence, a staffing crisis”, she replied: “A lot of it is.
“If I was to say that we need more beds in hospital to cope with increases in demand, then you have to staff those beds. You can’t just open the beds and expect staff to continue at the same level of care.
“Patient outcomes would be affected if you do that, we can’t do that lightly. So staffing really is crucial.”
Dr Evans highlighted that a reluctance to join the health profession could arise from ongoing “uncertainties” around pay and the decision of some to leave the sector.
“What we have often is an investment in our health services, which can sometimes be a little sporadic – sometimes it comes, sometimes it stops,” she said.
“What really would be great would be to have a long-term plan for our workforce and sustainable investment to make that happen.
“I think with that confidence and certainty, then it provides a much better, stable basis for staff to come and work in the NHS.”
Health Secretary Humza Yousaf echoed her sentiments, adding: “Staffing and workforce are absolutely critical.”
Appearing on the same programme, Mr Yousaf was asked how the Scottish Government intends to mitigate the impact of nurses leaving the profession amid a waiting time crisis and backlogs for NHS treatment.
He said: “The vacancies are far too high. So filling up a leaky bucket isn’t going to help, hence why there’s been so much focus from us on retention, and that’s why pay and terms and conditions are so important.
“We have the best-paid staff as you know, and I’ve said many times in your programme, here in Scotland.
“It’s also why I’ve offered a record pay deal. One that is the single biggest pay deal ever offered to NHS staff in a single year in the history of devolution.
“So we’ll do what we can around the workforce, but the bed capacity really is where so much of our focus is currently going.
“To try to even get a fraction of those 1,800 delayed discharges out of the system will free up much-needed bed capacity in our hospitals that are really feeling under pressure.”
He also warned that the past week has been “one of the most difficult” to have been faced by Scotland’s health boards.