Shaq's decision to pass on signing 'NSYNC after helping the boy band get off the ground is still tearing up Lance Bass' heart -- but he says there still would've been one major issue.
We got the singer at Villa Blanca in Bev Hills and our guy asked about Shaq coming thiiis close to signing 'NSYNC and the Backstreet Boys way back in the '90s.
Shaq's already said not signing the group is one of the biggest mistakes he's ever made, and Lance told us ... he couldn't agree more.
As you know ... 'NSYNC owes a lot of its early success to Shaq. Lance revealed their connection a couple years ago, telling us the NBA superstar lent them the recording studio in his Orlando mansion when they were starting out.
Lance says he 100 percent wishes the big fella pulled the trigger and signed them -- but adds he's not certain Shaq could've saved them from manager Lou Pearlman and his infamous ponzi scheme.