It's been debated. Giancarlo Esposito thinks it's possible, as does Vince Gilligan. But Gilligan also says he prefers for things about character's pasts to be vague and up for audience interpretation. 
The theory stems from Hector gay-baiting Gus and Max in the flashback when Max got killed, (saying something like they…

But this kind of thing was happened before on the show, more than once. It's in keeping with old school season one and two stuff.

But this kind of thing was happened before on the show, more than once. It's in keeping with old school season one and two stuff.

Mike was in the diner?

Mike was in the diner?

This won't be terribly relevant after Walt kills him.

This won't be terribly relevant after Walt kills him.

They've done several goofy "heist" scenes throughout the series' run. This might be our last one. Enjoy it.

They've done several goofy "heist" scenes throughout the series' run. This might be our last one. Enjoy it.

I'm not being passive-aggressive. It's just amazing to me. Even Bryan Cranston in interviews has marvelled at the totally irrational Skyler hate. The fact that you think Skyler and not Walt is the one who needs forgiving is mind-blowing. Walt broke back into the home and calmly sat at the table and played hero to Jr…

I'm not being passive-aggressive. It's just amazing to me. Even Bryan Cranston in interviews has marvelled at the totally irrational Skyler hate. The fact that you think Skyler and not Walt is the one who needs forgiving is mind-blowing. Walt broke back into the home and calmly sat at the table and played hero to Jr…

I think Marie finds out somehow and Walt has to kill her.

I think Marie finds out somehow and Walt has to kill her.

Bitches, man. Amiright? High Five!

Bitches, man. Amiright? High Five!

Saul didn't poison Brock. Walt did. It's still unexplained how exactly (which still bothers me, a year later) but this conversation confirms that it wasn't Saul. Otherwise, it's as you say, nonsensical.

Saul didn't poison Brock. Walt did. It's still unexplained how exactly (which still bothers me, a year later) but this conversation confirms that it wasn't Saul. Otherwise, it's as you say, nonsensical.

Forget it. You can't talk to the Skyler (read: woman) haters.

Forget it. You can't talk to the Skyler (read: woman) haters.

…aaand the crazed Skyler-haters start coming 'round. Wow.