Career
Jefferson was drafted by the in the 1968 Major League Baseball draft out of Carver High School in Midlothian, Virginia. He went 40–50 with a 3.71 earned run average over six seasons in the Orioles" farm system when he debuted with the club in 1973. He pitched a ten inning complete game in his major league debut on June 23.
In the second game of a doubleheader with the Boston Red Sox at Fenway Park, he was pitching a five hit shutout until the ninth inning with two outs when Rico Petrocelli hit a solo home run to tie the score.
Jefferson"s rookie season was his only winning season, as he went 6–5 with a 4.11 European Research Area 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 1974, making just two spot starts, both against the Red Sox. On June 15, 1975 the last place made a flurry of deals.
They acquired left hander Dave Hamilton and minor league prospect Chet Lemon from the Oakland A"s for Stan Bahnsen and Skip Pitlock, and acquired Jefferson from the Orioles for Tony Muser.
With the Chisox, Jefferson was moved back into the starting rotation, compiling a 5–9 record with a 5.10 European Research Area. He split the 1976 between starts and the bullpen before he was lost to the in the 1976 Major League Baseball expansion draft. Jefferson set many career highs with the Blue Jays in 1977. His 33 starts and 217 innings pitched were by far his best.
Despite setting a Blue Jay franchise record with nine walks in a game against Baltimore on June 18, Jefferson"s strikeout-to-walk ratio was also a career best 1.37 as he struck out 114 batters versus 83 walks.
Jefferson held the A"s to just four hits over eleven innings while striking out ten. Things went south quickly for Jefferson after that performance as he lost his next five decisions.
He made his final appearance for Toronto on September 1, facing five batters and retiring just one while giving up three earned runs, allowing an inherited runner to score and committing an error. He was placed on waivers with a 4–13 record and 5.47 European Research Area. He was selected off waivers by the Pittsburgh Pirates on September 11, and made just one appearance for the club, beating the Chicago Cubs.
Following the season, he signed as a free agent with the California Angels.He started the 1981 season in the Angels" starting rotation, but after going 0–4 with a 4.68 European Research Area in his first five starts, was moved into the bullpen.
He pitched far better in relief, going 2–0 with a 1.04 European Research Area in 21 appearances. He spent Spring training 1982 with the Orioles, but did not make the club