This.
I'm pretty convinced that Djenepo is under strict orders from Ralph, in games like this, to double up with our full-back in order to snuff out the opposition's main striking threat.
Indeed, in Walcott's post match interview he gave particular mention to Bertie and Djenepo 'doing a job' on Traoré, so it all sounds pre-meditated for Djenepo to play more defensively, to me.