We got the former Giants wideout at Catch in L.A. earlier this week with his "I AM ATHLETE" co-host Channing Crowder ... and the guy couldn't help but gush about Dallas despite his past feelings on the team.

"The last two months," Marshall said, "I've shifted. I think they're a true contender."

As for why he believes the Cowboys have gone from a 6-10 squad to now a true threat in the NFC?

"Dak Prescott healthy. Defense, middle of the road -- Super Bowl!" he said.

Crowder, though, ain't convinced ... the former Miami Dolphins linebacker said he believes it'll take Dak Prescott a full TWO YEARS to bounce back from his gruesome ankle injury.

"You recover from injury two years after the injury," Crowder said. "I don't think Dak's going to be back this year."

We also talked with the guys about Deshaun Watson ... and they told us they hate the idea of the quarterback currently being listed as the fourth string on Houston's depth chart.

The two agreed that if the NFL won't put Watson on paid leave amid sexual misconduct allegations ... the Texans should either start him or trade him to another team that will.

By the way, the dudes are KILLIN' IT with their "I AM ATHLETE" show ... and after talking ball with us, they promised big things are coming with the show and the brand in the near future!