Per Chip Scoggins of the Star-Tribune, the defending NFC North champions are "hoping" to retain Diggs and Barr.
Thanks to their ability at drafting and developing franchise players on both sides of the ball, the Vikings find themselves in a difficult position of having to pay a lot of talent at roughly the same time.
Scoggins noted the Vikings have already re-signed Harrison Smith, Everson Griffen, Xavier Rhodes, Linval Joseph and Eric Kendricks in the past two years. That doesn't include the three-year, fully-guaranteed $84 million deal given to quarterback Kirk Cousins as a free agent in March.
Minnesota currently has $15.2 million in cap space for this season and $31.9 million available for 2019, per Over the Cap.
Diggs and Barr are entering the final years of their rookie contracts.
Barr, who was drafted ninth overall in 2014, has made three straight Pro Bowl appearances and set a career high with 75 combined tackles last season.
Diggs tied for the team lead with eight touchdown receptions in 2017.
The Vikings have high hopes for 2018 after going 13-3 and reaching the NFC Championship Game last season.