Jefferson was drafted by the new club away from the Chicago White Sox, for whom he pitched in 1976 and part of the 1975 season.
In the first season of Major League play, he pitched pretty well for an upstart team, posting an earned run average of 4.31 with eight complete games over 33 starts, with 217 innings pitched.
Of course, as with any club just starting out, he wouldn’t get any support as evidenced by his final record of 9-17.
He would put together a nine-year career in the Big Leagues, finishing with a record of 29-81 along with an E.R.A. of 4.81 over 237 appearances, 144 of those starts, with four shutouts and 522 strikeouts in 1085.1 innings pitched.