The newspaper report that Tottenham are eyeing Johnstone, who has spent the last one-and-a-half seasons on loan at Aston Villa, as a potential back-up to Hugo Lloris.
The Sun claim that current option Michel Vorm, 34, may leave Tottenham this summer as his contract comes to an end, with the senior man having spent four seasons at the club as second-choice goalkeeper.
It is said that Johnstone is also out of contract this summer and so may move on a free, although United are known to have an option to extend his contract by another year.
Good move for Tottenham Hotspur?
Johnstone has shown himself to be the standout goalkeeper in the Championship this season, and would be a brilliant back-up to Lloris.
The kind of form that the 25-year-old is in for Villa may even propel him to bigger things at the club, with some believing that Lloris is in decline.
If Johnstone is available for free, then this one is a no-brainer, and Spurs would do well to secure his signature.
This is Futbol rating: 8/10
Likely to happen?
It is unfortunately unlikely that Johnstone would accept a role as a number two.
The 25-year-old has now had a taste of regular football at a big club after seven loan spells during his time at United, and will hardly want to go back to sitting on the bench.
Unless Tottenham are planning to replace Lloris soon, then this one looks a non-starter.
This is Futbol rating: 2/10