T.J. Dillashaw Doesn't Seem Like a Cheater, Says 'Wonderboy' Thompson

UFC's Stephen "Wonderboy" Thompson says it's "disappointing" his friend, T.J. Dillashaw, tested positive for a banned substance ... saying, "He doesn't seem like the type of guy who would do that."

Dillashaw has already relinquished the UFC bantamweight championship after officials say he failed a PED test following his January fight against Henry Cejudo.

And, while officials aren't identifying the substance they allegedly found in Dillashaw's system, Thompson says the situation is a reminder to fighters to be very careful what they put in their systems.

"I know T.J. We've hung out a lot. He doesn't seem like the type of guy who would do that," Thompson says.

"But, that goes to show man, you gotta check everything that you take."

It's obvious Thompson doesn't think Dillashaw intentionally cheated -- and says he hopes T.J. can "get this thing worked out."

For now, T.J. has been suspended 1 year by the New York State Athletic Commission. Dillashaw says he's conducting his own investigation to find out what went wrong.