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When the going gets tough, you DON'T REQUEST A TRADE -- so says Terrell Owens who says Sam Bradford's antics in Philly are straight up cowardly.

T.O. was hangin' at The Grove in L.A. when we asked the ex-Eagles superstar who should start for the Birds at QB this season ... Bradford or rookie prodigy Carson Wentz?

"It's Sam Bradford's job to lose," Owens said.

But when we started talking about Bradford's trade demand -- T.O. busted out the real talk.

"I think it was not a great move for Sam to want to request a trade being that they were getting a #1 pick."

"If it were me ... that's kind of a sign of a coward, to be honest."