The 22-year-old showed fans how hard he's been working.
The 22-year-old, who has regularly been criticised for his poor fitness while at United, followed up the post by replying to a fan's tweet and showing his determination ahead of the 2018/19 campaign.
Am not finished yet— Luke Shaw (@LukeShaw23) July 6, 2018
The Englishman has failed to live up to expectations since he arrived from Southampton for £27 million in 2014 and has long been a subject of debate amongst United fans.
Some have criticised Jose Mourinho's treatment of the left-back and consider that to be a key factor behind Shaw's poor development, while others believe the defender's poor attitude is to blame.
Shaw has made 66 appearances for United since joining the club but has been unable to hold down a first-team place.
The England international has experienced some bad luck with injuries, particularly at the beginning of the 2015/16 season, when, having started the campaign playing his best football in a United shirt, he suffered a nasty double leg break against PSV Eindhoven.
With Ashley Young coming off a fantastic year last season, and the Daily Star reporting Alex Sandro is close to joining the club, Shaw will have to work hard for first-team opportunities, but the fans appear to be impressed by the work he has shown so far and are backing him to make an impact moving forward.
Yes Luke! Buzzing to see you back in pre-season!— United Xtra (@utdxtra) July 6, 2018
Go on Luke.. We're all behind you.. Nothing more than we want to see you have your best season @ManUtd— Phil (@philstandish) July 6, 2018
Got to be honest. I questioned your professionalism seeing those first pictures but I am delighted to see you have proven me wrong. Need a big season from you Luke, you could be our Left Back for the next 5-10 years, show us how much you want it— Jonny (@MancJohnson) July 6, 2018
You make some of us who have defended you all this while feel vindicated and proud. You’ll be the best LB in the world. Just keep working Luke. We have your back.— Richard Arina (@raphael223) July 6, 2018
Great to see, really hope the upcoming season is a great one for u, staying fit and injury free,knuckle down and own that LB slot— Paul Wade (@paulmatthewwade) July 6, 2018
Come on lad! Let’s see the real Luke Shaw!!!!— Dave Allen-Ashcroft (@DaveAAshcroft) July 6, 2018
C'mon fella.. United fans are gagging to see you as our left back for next 10 yrs....— Tony Bell (@tbelly7) July 6, 2018