It needs to be determined whether Duffy is good enough... If he is, we either need to 1. get him actual playing time this year, 2. Loan him out to a PL club (a Championship loan won't do it frankly)... If he isn't, he should be sold or loaned out until his contract expires in May (I believe he has one year left).
*Edit* It will be interesting to see how Garbutt, Ty Browning could get involved, even if they are determined to be good enough given that Garbutt is our third choice left back (a position that doesn't really need to be rotated... Frankly, we could struggle to get Oviedo enough time, much less Garbs), and Browning given that he's behind Coleman at rightback and 4-5 other players at centerback.