Joe Nichols may have a whole list of hits to write home about, but the 'Gimmie That Girl' singer can't stop thinking that 'Who Are You When I'm Not Looking' is the one that got away. Nichols called into KMPS in Seattle on Friday while waiting to board a plane to Cancun to chat about Blake Shelton and his own 'Greatest Hits' album, which dropped on Jan. 25.

Fellow country star Shelton is currently seeing great success from 'Who Are You When I'm Not Looking,' which he recently released as a single from his 2010 album, 'Loaded: The Best of Blake Shelton' -- but Nichols originally recorded the song for his 2007 release, 'Real Things,' and wishes it could have been his single first.

"Blake did a great job with that song," Nichols says, giving credit to the 'Hillbilly Bone' singer. "I've been a fan of that song for a long time and I'm glad to see it has found a home, and that he's having a great big hit with it."

"I wish it could have been us," he adds, laughing.

"I begged for that single. I wanted that single so bad," Nichols admits. "But sometimes they don't listen to little old guys like me. I'm happy for him [Shelton] because it's a great song -- and who better to sing it than Blake? He nailed it."

Nichols shouldn't feel too bad -- his new music video for 'The Shape I'm In' is getting lots of talk as it climbs into the top 5 of CMT's Top Videos. Listen to both Nichols' and Shelton's versions of 'Who Are You When I'm Not Looking' below, and let us know which is your favorite.

Listen to Joe Nichols' 'Who Are You When I'm Not Looking'

Watch Blake Shelton Perform 'Who Are You When I'm Not Looking'