Mastrogiovanni, a three-star and No. 18 linebacker in the country, was OU's eighth commit in the class after pledging way back in June 2012.
He stated as recently as Dec. 26 with FOX Sports NEXT's Ahmard Vital that he was excited about heading to Oklahoma.
"For me, I grew up a huge Sooner fan and I got to check out a lot of programs and I just felt at home most at Oklahoma," said the 6-foot-2, 230-pound backer who was at Jerry World watching his future teammate and defensive end Matt Dimon, a current OU pledge, at the time.
But that will no longer be the case, as A&M not only knocked off OU the other night in the AT&T Cotton Bowl Classic, but steals another prized target from the Sooners in the last month.
In recent days, they locked up a verbal from OU legacy defensive tackle Justin Manning.
Now, the Sooner recruiting woes continue.