Odom, 35, has been showing slight signs of improvement ever since he came to on Friday, Oct. 16, but a source said he has a long battle ahead of him. Before he opened his eyes and spoke, he'd been unconscious for nearly three full days.

READ: Lamar Odom found unconscious, airlifted to hospital

According to Us, the insider said:

"He's still getting better little by little. The doctors are starting to talk about plans for what happens when he gets out and that's how rehab came up, but he still has a ways to go."

Khloe Kardashian and her mother, Kris Jenner, arranged for him to receive further care in L.A., in part "so they can all be closer to him," the source said. He was picked up by helicopter on Monday evening.

READ: Khloe brings Lamar's father, children to his bedside

"It's all baby steps, very slow. Everything is going very slow," the insider added. "He's talking more. He's very slowly improving. It's going to be a struggle."

The Sixth Man of the Year winner has the support of family and friends including his ex Liza Morales, their kids, Destiny and Lamar Jr., his ex-teammate Kobe Bryant, and Khloe's many siblings -- ever since he was first hospitalized last week. So he won't be facing it alone.

Khloe, in particular, has hardly left the athlete's side. Though the two split in 2013, they're not yet legally divorced, and the Keeping Up With the Kardashians star has never fully lost touch with her ex.

"Khloe is committed to staying with him," the source said "It's a slow process, but Khloe is there every step of the way...It's all been so draining and emotional."