The Vikings' plan is easy to ascertain: Upgrade the offensive line after NFL rushing leader Adrian Peterson was held under 100 yards in five of the final six games of the 2015 season. To that end, general manager Rick Spielman added mauling guard Alex Boone and mammoth right tackle Andre Smith. Wide receiver remains a question mark after disappointing speedster Mike Wallacesigned with Baltimore. Although Stefon Diggs exceeded expectations as a rookie, he's more of a second fiddle as opposed to a legitimate No. 1 receiver.