Defender Jack Stephens has signed a two-year contract extension ahead of completing a season-long loan move to Middlesbrough.
The 21 year-old has extended his deal until the summer of 2019 and now joins Boro for the 2015/16 campaign.
Executive Director of Football Les Reed commented: “The move to Middlesbrough is a fantastic opportunity for Jack on the back of his successful spell in League 1 with Swindon last year.
“Our decision to hand him a new, long-term contract is a show of the club’s faith and trust in his development.
“Middlesbrough is a club with a good playing style and one likely to be challenging for promotion this season – an experience that Jack will surely relish.
“As with Sam Gallagher, who joined MK Dons yesterday, we will watch Jack’s progress closely and look forward to welcoming him back to the club next summer.”
Stephens added: “I’m delighted to extend my contract. This is where I want to be in the future, so this is a brilliant moment for me.
“This is a great opportunity for me to push on now. I loved going out on loan last season and getting the experience that I needed, and I think that’s shown since I’ve returned.
“It’s now important for me to play more games and improve as a player so I can come back to Southampton as a better player.
“There’s going to be a bit of pressure with Middlesbrough expected to get promoted, but that can only be a good thing for me.”