McKay, a left-handed pitcher and first baseman from the University of Louisville who won the Dick Howser Trophy as college baseball's top player this year, was Tampa Bay's top pick in the Draft. The 21-year-old was rated the No. 2 prospect available in the Draft by MLBPipeline.com.
The Rays' terms with McKay would be over slot value for the No. 4 pick, which is $6,153,600.
Tampa Bay said after drafting McKay that the team was open to letting him continue to be a two-way player. McKay is a 3-time winner of the John Olerud award for best two-way player in college baseball.