The 24-year-old joined Villa on a loan basis back in January and, following a shaky start, quickly got to grips with life in the Championship, prompting manager Steve Bruce to express hopes he would remain at the club on a permanent basis.
It was recently reported that Villa were lining up a deal, estimated to be worth around £3m, to sign the Englishman ahead of next season.
And according to Birmingham Mail‘s Joseph Chapman, a deal has been agreed between the two clubs over Johnstone.
One can hardly blame Johnstone for, at the age of 24, deciding to establish himself at a first choice keeper elsewhere. He arrived at the club as a youth player in 2009 before joining the first team as a third choice option back in 2011, but never made a senior appearance at Old Trafford.
Disappointing, of course, but without doubt the right thing for a keeper with too much potential to be sitting on the bench or playing for United’s reserves. The lessons learned at Carrington would have been invaluable, however, supporters will hope to see him thrive at his new club.