O'Neill was drafted in the second round by the Vikings in 2018.
The hope is he'll be ready for Week 1, according to the report.
An earlier report said Dennison had been let go.
The left tackle had said his goodbyes to his teammates.
Matthew Coller writes a weekly Vikings column for BMTN, with more of his work found at Purple Insider.
Any other Vikings fans feel the way Blair Anderson does?
Blair Anderson is a Vikings superfan who convinced BMTN to give him a blog.
Blair Anderson has a theme (bleep show) in his latest Wide Left blog.