[1] He represented the United States in baseball at the 1964 Summer Olympics as a demonstration sport, one of seven pitchers on the team.

Closter played only one game in the Senators organization, pitching 0.1 innings against the Baltimore Orioles in his MLB debut, before being purchased again by the Yankees on May 3, 1966.

In 1968, Closter began the season with the single-A Fort Lauderdale Yankees of the Florida State League.

[5] After making his Major League debut with the Senators in 1966, Closter wouldn't play another game in the MLB until 1971, when he made occasional relief appearances for the Yankees.

In his remaining two seasons in the MLB, Closter only made 6 appearances between the Yankees and Braves, pitching 6.2 innings in relief.