McManis also had an offer from UT-Chattanooga.
"I was looking forward to some offers from SEC schools this season, but I just went ahead and committed," McManis said.
McManis said he plans to bring a hard-nose attitude to the Tigers when he joins the team after his senior season.
"I want to get it on every play," he said. "I want to be a part of Memphis and getting it back on the map."
McManis is the second commitment in five days for U of M coach Larry Porter. Eric Belew, who is projected to play safety, committed to the Tigers last Friday.
McManis said a big factor in his decision was the U of M's recent commitment to a $10 million indoor practice facility.
"I know what Coach Porter's trying to do," McManis said. "I noticed some changes in the facilities and where Memphis is going. I like the direction and I want to be a part of it."