Cory Monteith's co-star is proud of him for entering rehab.

The 'Glee' actor's friend and colleague Mark Salling thinks he is very brave for dealing with his ''substance abuse'' issues publicly and has been sending him supportive texts while he seeks treatment.

The 30-year-old actor told on Saturday (06.04.13): ''It takes balls . . . to go through that publicly. Period. It takes balls to go through that privately, but to go through it publicly like that - balls.''

Mark said the entire cast has been trying to show Cory that they are rooting for him by sending him ''nice texts'' and tweeting ''here and there.''

Cory, 30, checked into a treatment facility on April 1 and announced he was seeking help from a ''serious problem'' with drugs and alcohol.

The actor - who has been clean since going to rehab at the age of 19 - was reportedly led astray by his Hollywood friends and started drinking and taking drugs at parties at his Hollywood Hills home.

The source previously explained: ''He drinks hard and then he can't say no to other things. The house party scene in Los Angeles is dangerous for him. He thought he could dive in and then drop it but he got hooked on stuff again.

''Rehab can work for him because he's committed. He feels blessed with his life. He realised he needed outside help and he really wants to get back on track.''

Cory's girlfriend Lea Michele, 26, has been praised by his friends for being a really good influence on him.

An insider recently said: ''Lea is an excellent influence on him. She's good for him. She's really calmed him.''