After a 13–17 season with a 2.77 ERA in 1968, Jackson was selected by the Montreal Expos in the October 1968 expansion draft, but chose to retire rather than join the team; Bobby Wine was sent from the Phillies to the Expos the following April as compensation. In a 14-season career, Jackson posted a record with 1,709 strikeouts, 37 shutouts, and a 3.40 ERA in 558 games and innings. He tied a record held by Claude Passeau by four times having the most total chances among pitchers with a perfect 1.000 fielding percentage (1957, 1964, 1965, 1968).