Dummett will still most likely be the starting LB next season (unless Rafa doubts his ability to play consistently and at a high enough quality for the top tier), but there are questions over who he would rotate with for cover.
Lazaar has failed to make an impact and challenge Dummett for a place in the starting XI, which is horrifically concerning, and Haidara has a horrid injury record which cannot be relied upon throughout the season; Baba Rahman would be a good option on the left side.
Signed for Chelsea in the 2015 summer transfer window from Augsburg for a starting fee of £14 million (rising to £22 million depending on certain factors), Rahman played over 1000 minutes of English football in his first season, contributing one assist.
This is significantly less to the previous season in the Bundesliga where he scored twice and assisted six times in 33 appearances. In an attempt to revive his form and get more game time he was sent to Schalke 04, but unfortunately, he suffered an ACL injury midway through the season but still netted once and assisted twice in 21 appearances.
NUFC should take a gamble by signing the young Ghanaian. His high potential, versatility to play anywhere down the left and attacking output should offer more than Dummett. Chelsea will more than likely loan Rahman to a Premier League club to get more minutes in English football, so linking up with his international teammate could be on the cards.