Ferdinand described it as "unsettled".
He wrote in the Mail on Sunday: "Unsettled is perhaps a good description of our club season. We weren't playing well and those fluctuations in consistency take their toll. United fans rightly want success and it gets stressful for everyone when it's elusive.
"The pressure mounted. Questions started to be asked about David Moyes's future as manager. That adds pressure all round. Who might he buy? Who would play? Was he even staying, or going?
"We didn't know. He didn't know. After 27 years of Sir Alex Ferguson, that uncertainty was a shock at United.
"It was always going to be a tough season. Moyes replacing Sir Alex has to be the toughest gig in football."
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