Jefferson's rookie season was his only winning season, as he went 6–5 with a 4.11 ERA as a spot starter and middle inning relief pitcher. The Orioles captured the American League East crown, and manager Earl Weaver had Jefferson slated to be his long reliever in the post season, but he did not make an appearance in the 1973 American League Championship Series with the Oakland Athletics. Jefferson moved into the bullpen in , making just two spot starts, both against the Red Sox.