Shaw was selected to play for the international duty even with his lack of playing time as he’s been regularly overlooked since his return to fitness in mid-January.
His future at Old Trafford still remains uncertain, even though Mourinho claimed there’s no chance he’ll be sold in the summer as he’s the long-term option at left full-back.
Speaking about his future, Southgate claims Shaw needs to work hard and focus.
“That’s for him and his club to deal with. He has got a challenge now to get himself into the team there,” he said.
“I think Luke’s sole focus has got to be how can he get himself back in the team if he is not in the team.
“There’s a challenge for every player. We want competition for places, we have got competition for places in every area of the field.
“If you are at a club like Manchester United, that’s going to be the same so as an individual how are you going to do everything you can to get back into the side?
“People say that managers pick teams, but really players do because of the way they train, the way that they are, the way they play.
“They make your decisions as a manager so that is the challenge Luke has at the moment.”
“In an ideal world, you have all your players playing and playing at the highest possible level and playing in Europe and everything else.
“But we have got to be open-minded because we want the right characters through the door and there are moments when a player isn’t playing for his club, like with Luke (Shaw), where you think this might just give him a bit of a lift, a boost.
“I don’t want to have a hard and fast rule because I might break that in the future at some point.”
It’s a well-timed boost for Shaw and hopes are Southgate’s tactics work as he looks to get the best out of the Englishman when he returns back to Old Trafford.
He’s by far our best left-back and we’ve seen it with Anthony Martial and Henrikh Mkhitaryan as they both returned from time on the sidelines as much better players.