Darren Waller says he's 100% there for Aldon Smith in his transition back to the NFL if the new Dallas Cowboy needs him ... telling TMZ Sports, "I'd definitely be open to talking to him."
Waller, like Smith, battled substance issues early in his NFL career ... but got sober and turned into a dominant force with the Oakland Raiders this past season.
30-year-old Smith is trying to replicate that accomplishment with the Cowboys after being out of the league since 2015 ... and Waller says if the former All-Pro needs advice, his phone line is open.