The 26-year-old singer released the song with former One Direction member Zayn Malik and Usher over the weekend. Brown apologizes to Tran in his verse, letting the 27-year-old model know he still misses and thinks about her.
"Now where you been, it's been a year/Baby I ain't seen you, you know I miss you/Baby let me love you back to sleep once more.
And I know we don't speak no more/But I just wanna tell you I'm sorry/For [expletive] around with Keisha and MaKala/For all the Georgia peaches in Decatur/For all these [expletive] in the elevator.
I just want you to love me/Yeah baby don't test me/You know I'll do it/You want me to say your name, girl?/Okay, Karrueche!"
Brown and Tran split in March after the rapper discovered he fathered a daughter named Royalty with Nia Guzman. Sources told Hollywood Life Tran was "flattered" by Brown's verse but is "doing her best to keep her guard up."
"He just won't stop trying to get back into her good graces," the insider said. "No lie, she's flattered he mentioned her in his song. It caught her off guard but she felt it was real and genuine and she appreciates it."
Brown and Tran were an on-again, off-again couple for several years and previously broke up due to the rapper's lingering feelings for Rihanna. Brown discussed the possibility of a reconciliation in July, but told Ryan Seacrest he isn't actively pursuing Tran.
"Us getting back together, I can't say," the singer said. "I don't know what the future holds. As of right now, I am just completely focused on myself. I'm not trying to date anybody. I just want to figure me out and grow within myself."
The original version of "Back to Sleep" appears on Brown's seventh studio album, Royalty. The record debuted at No. 3 on the Billboard 200 in December and also includes the singles "Liquor" an "Fine by Me."