According to The Athletic, the Saints are in the market for a left-back as they only have Romain Perraud as their only senior option.
The 21-year-old spent last season on-loan at Norwich City and made 26 appearances for the side. Despite some impressive displays from the youngster, the Canaries finished bottom of the table and never really looked like surviving in the Premier League.
Williams still has two years remaining on his Manchester United contract, but he is at best fourth-choice left-back now following the arrival of Feyenoord starlet Tyrell Malacia. The Dutchman will compete with Luke Shaw and Alex Telles for a place in Erik ten Hag's starting lineup.
The England U21 international made his first-team debut for the Red Devils in 2019, 11 years after joining the youth academy of his boyhood club. He has since played 50 times for United, scoring once.
Williams has not joined the United squad for their pre-season tour of Asia and Australia, leading to speculation that he would soon be leaving the club. However, in a defiant Instagram post, the young defender posted:
"My injury, I told myself to deal with it and bounce back stronger. My goal is to play in-front of the best fans in the world."
Brandon Williams will be "looking over his shoulder" at Manchester United after new signing: Paul Robinson
According to former England goalkeeper Paul Robinson, Williams will be concerned for his place at United following the arrival of the “very, very good” Malacia from Eredivisie.
Speaking to Football Insider, the retired Tottenham shot-stopper proclaimed:
“I think Brandon Williams will be looking over his shoulder at that signing. Luke Shaw has had his injury problems. Erik ten Hag is exploiting the Dutch market. He knows the league.
“I covered a lot of the Eredivisie last year for a broadcaster and I was impressed. There is a lot of talent in that league. It is about finding the right players for the right price."
“Malacia is a very, very good player. He will provide competition for Luke Shaw and Alex Telles. All can play in the wing-back position or as a left-back in a four. It gives the manager another opportunity to add competition for places. It is a work in progress. They need players.”