So here's a still from Friday's walkthrough video:
Watch the thing in full if you need to assure yourself that this is not a hallucination and is actually a bandage on his elbow.
What is it? Denard had a procedure earlier this week for an abscess on said elbow. The bandage is the after-effect. An abscess is an irritating, fairly quick-healing thing that may have affected his accuracy earlier in the year. It won't cause him to miss any time but may be a reason the passing game has been minimized so far. If he suddenly gets a lot more accurate in three weeks that might be why.