The Scotland captain has contracted ulcerative colitis - a chronic inflammatory bowel condition – and is now resting on medical advice.
Here is a selection of the posts we have received so far on our message board - feel free to add your comments at manutd.com/talkingreds.
Rooney7: "Get well soon, Darren, we need your 110% effort in our squad."
Nr10Rooney: "I'd like to say get well soon, Darren. It's important to take a break from football as what you have is hard - I know because I had it for 15 years! Best wishes and I hope you get over this."
StevieP: "I know all about ulcerative colitis as I contracted it in my late teens. I am now 60 and have been free of it for 30 years. I am married with two children and play golf three times a week so there is life at the end of the tunnel. Good luck for a full recovery Darren, from a lifetime Red."
FTUnited: "It goes without saying that your health is your wealth. Mind yourself Darren and get well soon."
Otto Licha: "I wish Darren all the best for his health and hope he will be back soon, not only as we are lacking midfielders but because he is a great guy with a United heart."
RangerMaj: "As a United fan, I want to send my sincerest best wishes for a speedy recovery. I have had similar issues myself so I understand the challenges. I am certain he will overcome them."
Ariana99: "I remember when he produced man of the match performances against the likes of Arsenal, City, Chelsea and AC Milan. Hopefully he will recover and enjoy more outstanding