Merriam-Webster Dictionary of English Usage:
Copperud 1980 terms this verb "journalese," and William Safire publicly apologized in his New York Times column of 24 July 1983 for using it. New York journalists seem a bit diffident about using compound words of which adverbs form the first part (see, for instance, UPCOMING).
Downplay is a relatively new verb, evidently going back no farther than 1954. It's main use does seem to be in jounalism: almost all of our evidence comes from newspapers and magazines. Thirty years in the business seems to have established it for genereal use. Here is a cross-section of our evidence [omitted].