Cardi B -- who has the #1 song in the country -- says NFL owners need to hire Colin Kaepernick ASAP or she'll boycott NFL Sundays and start watching baseball instead ... on whatever day baseball is on. 

The "Bodak Yellow" rapper told Billboard that people need to stop pressuring the NFL players to boycott because they need to make a living ... the real pressure needs to be on the owners. 

"You can't really be mad at the players," Cardi said ... "These people need their jobs too. Are you gonna pay them? Be mad at these goddamned team owners."

She also trashed Trump -- referring to him as "Carrot Face."

As for Colin, he's in game shape -- at least he looked buffed up and ready to play out in NYC on Monday morning.