David Ortiz is still mourning the death of Tim Wakefield ... telling TMZ Sports this week his former Red Sox teammate was a "great guy, man."
"Great guy," he repeated.
Ortiz opened up to us about Wakefield for a few moments while out in Los Angeles ... just days after the former Boston star pitcher died from brain cancer.
Big Papi said the knuckleballer was straight-up "like my family, man" ... and you can see in the clip, he's obviously still in pain over the passing.