Luke Shaw
Luke Shaw in action for Southampton against Chelsea. [Reuters]

Manchester United and Chelsea have suffered a blow in signing Southampton full-back Luke Shaw in the ongoing transfer window. The Saints manager Mauricio Pochettino warned the Premier League pair that his side will not allow the defender leave the club.

The 18-year-old came up through the ranks of Southampton's academy and has been in brilliant run, since making his way to the first team in 2012. The Mirror reports United and Chelsea have long maintained their interest in signing the defender.

David Moyes has the services of Patrice Evra as the first choice left-back in the squad and the Frenchman has less than six months left on his contract at Old Trafford.

The Blues are looking to replace Ashley Cole as Jose Mourinho has set his eyes on Shaw as a replacement for the former Arsenal left-back.

Southampton manager had earlier admitted that Shaw will not be sold in January. Pochettino has once again re-iterated his side's desire to hold on to their star player and revealed that the club has no intention to allow the English defender leave this month.

"He hasn't said anything to me that has changed the situation from when he said he wanted to stay. It is still the same. At this moment Southampton have no interest in selling him. Not in the summer either," Pochettino explained.

"Southampton has many great players for the future. We have no ambition of selling any of them. As far as I know we have had no interest. I don't expect any phone calls either," he added.

The former Everton manager could turn his attention in signing Real Madrid defender Fabio Coentrao, who has long been a transfer target for the Premier League champion.

Meanwhile, Chelsea have allowed Ryan Bertrand to join Aston Villa on loan. The England international believes his move to Villa Park will be crucial for progressing in his career.

"I have always looked for progression in my career. Since I was back at Chelsea after being on loan for so long I have gone from 15 games to 20 odd to 30 odd. I couldn't see that progression again this season. As soon as the alarm bells started to ring I knew I needed to fix it," Bertrand said.