A power-hitting outfielder whose career was hindered by phlebitis,[1] Greengrass appeared in 504 games over five seasons (1952–56) in Major League Baseball (MLB) for the Cincinnati Reds / Redlegs and Philadelphia Phillies.

Finally, on August 28, 1952, the pennant-bound Yankees packaged Greengrass, who had spent the season in the Double-A Texas League, three other players and cash in a trade to Cincinnati for the Reds' former All-Star pitcher, Ewell Blackwell.

Greengrass shares with Pop Dillon the record for the most doubles hit on the opening day of the Major League Baseball season, with his four two-baggers on April 13, 1954.

On the following day, April 30, he was traded to the Phillies in a three-for-three deal, and celebrated his arrival by getting two hits and his first 1955 home run in his Philadelphia debut on May 1.

His problems with phlebitis began that season[1] and he struggled through the 1956 campaign, his last year in MLB, hitting .205 with five homers as a backup outfielder.