BASEBALL American League * Orioles -- Placed Ben McDonald (pitcher) on the 15-day disabled list. Signed Ernie Whitt (catcher) and Paul Kilgus (pitcher). Optioned David Segui (first baseman) and Roy Smith (pitcher) to Rochester of the International League. Optioned Bob Milacki (pitcher) to Hagerstown of the Eastern League.
* Toronto Blue Jays -- Optioned Rob Ducey (outfielder) to Syracuse of the International League.
National League * Pittsburgh Pirates -- Signed Andy Van Slyke (outfielder) to a three-year contract extension through 1994.