In St. Louis and thinking of booing Albert Pujols in his return to Busch Stadium this week??

Don't do it ... so says Cardinals star Matt Carpenter, who tells TMZ Sports Pujols deserves to be treated like a king in his first game back in STL.

"Like a hero coming back to town," Carpenter says.

Of course, The Machine famously put together a Hall of Fame career for the Cards from 2001 to 2011 ... but he didn't leave for the Angels on the best of terms following the '11 season.