Phillips tore the anterior cruciate ligament in his right knee during Sunday's NFL Hall of Fame Game in Canton, Ohio, in which the Cowboys defeated the Cincinnati Bengals 16-7.
The second-year pro, who was vying against Martellus Bennett for the backup tight end spot behind Jason Witten, hauled down four passes for 60 yards before leaving the game in the second quarter.
Dallas took Phillips, 23, in the sixth round of the 2009 draft out of Virginia. He caught seven passes for 62 yards in 16 games last year as a rookie.
Notable deaths of 2014 [PHOTOS]