Mentor's 5-game winning streak ended on Dec. 29.
Cardinals coach Bob Krizancic said his team needs to be more aggressive to avoid a losing streak in Nashville.
Mentor shot 6 of 25 from 3-point range and were unable to get tempo in its favor while falling to host Christ Presbyterian Academy, 69-54, on the opening day of the CPA Next Level Hoop Fest.
It was the first loss for the Cardinals since opening night in overtime vs. Garfield Heights.
"We were tentative. We need to be much more aggressive against these teams down here," Krizancic said.
"(CPA) was good. They hit some shots. But we have played teams like that before. We just needed to be more aggressive against the press than we were. We needed to attack and we didn't do that. These guys knew coming down here what we were getting into with this competition. We will need to be very good the next two days."
Mentor (5-2) fell out of the winner's bracket and will play Episcopal Collegiate (AR) at 5:30 p.m. on Dec. 30 in Round 2.
Junior center Micah Potter led the Cardinals with 25 points and seven rebounds. Mentor was outscored in each of the first three quarters and trailed, 55-34, heading into the fourth quarter.
Austin Koss came off the bench and hit three 3s for the Cardinals and finished with nine points. No other Mentor player had more than five points.
Braxton Blackwell, a D-I recruit from CPA had 20 points. Micah Davis hit six 3s and finished with 18 for the Lions.