The talented full-back broke into United's first team in 2015/16 under Louis van Gaal but new boss Jose Mourinho sent him out on loan to Wolves last season.
At Wolves he appeared to go backwards, becoming ostracised by then manager Paul Lambert who took over from Walter Zenga in the Autumn.
Borthwick-Jackson now has a second chance to prove himself a Championship success, by helping Leeds United's promotion challenge.
He is likely to be thrust into first team action after first choice left-back Gaetano Berardi appeared to suffer a dislocated shoulder.
A loan move is best for Borthwick-Jackson's career, but the choice of club is what has upset Manchester United fans.
Manchester United and Leeds United have years of bitter rivalry behind them, even though it has slipped somewhat due to the Yorkshire club's exile from the Premier League.
Yet bitter feelings still exist, with more than one Manchester United fan urging Borthwick-Jackson 'not to bother coming back'...
Leeds? Don't bother coming back, Cameron.— Dylan (@RockNRolIStar) August 7, 2017
Leeds? Ffs!— Harjeet Randhawa (@randhawamufc) August 7, 2017
Did he have to go to those scumbags?— Rhys Grant (@Bluebird131999) August 7, 2017
Don't ever come back then!— Callum (@Callummufc23) August 7, 2017
Don't give our players to that pathetic excuse of a club— HalfPotatoHalfMonkey (@RojoTackles) August 7, 2017
Why them? He's better than Leeds ffs— • (@ElDiabloRojo__) August 7, 2017
That's a bad move sending him to Leeds— Jevan fletcher (@jevan_fletcher) August 7, 2017
Wow how things have changed! I suppose we owe them one for selling us King Cantona for £1million. How much would he be worth today!— IronFish (@PaulJamesSalmon) August 7, 2017
That's a shame. He needs a chance in the first team. Our only specialist LB with Shaw injured. #ManchesterUnited— Sam Pinson (@SamPinno) August 7, 2017