Vikings 'asking a lot' from rookie receiver Olabisi Johnson

One Vikings rookie might have locked up a roster spot ahead of Thursday's preseason finale in Buffalo.

Receiver Olabisi Johnson practiced with prominent Vikings players this week during separate morning sessions, designed by head coach Mike Zimmer to rest veterans in the afternoons, when the rest of the team has practiced.

Johnson, a seventh-round pick (247th overall) out of Colorado State, has caught five of six targets for 87 yards and a touchdown this preseason, perhaps earning him a spot in the receiver race behind Adam Thielen, Stefon Diggs and Chad Beebe. Johnson's 36-yard kickoff return against the Cardinals showed he could also be an asset on special teams, having returned both kicks…