We can rule out travel for the reason as to why Tom Brady and Rob Gronkowski have been missing OTAs.
According to the Boston Herald's Karen Guregian, both Brady and Gronkowski were at TB12 Monday, which is located at Patriot Place right next to Gillette Stadium.
Brady's absence from OTAs is notable, as the quarterback has not only gone to them in years past, but stressed their importance as it relates to preparing for the season. The two skipping out on OTAs does little to quell concerns about rifts between the Patriots and their star players.