Longtime MLB announcer Jim Kaat is in some scalding hot water ... after he shockingly made a slavery reference while calling the Astros vs. White Sox ALDS playoff game Friday.

Kaat's comment came in the 2nd inning of Game 2 as Chicago infielder Yoan Moncada stepped up to the plate ... when co-announcer Buck Showalter shared a story about the first time he saw the 26-year-old Cuban star in person.

The ex-Orioles manager said he remembered asking the Baltimore front office, "Can we have one of those" ... to which Kaat replied, "Get a 40-acre field full of 'em."