Standing and , Stoneman was a workhorse who over four consecutive seasons (1969–72) logged more than 200 innings pitched. He struck out 251 in 295 innings in 1971, with a 17–16 record and a 3.15 ERA for non-contending Montreal, 71–90 (). Stoneman was third in strikeouts in the National League in 1971, behind Tom Seaver (289) and Ferguson Jenkins (263), and his 39 starts tied for the league-high with Jenkins. He also had 20 complete games in 1971, tied for third with Bob Gibson. His career was shortened by an arm injury in 1973: his earned run average ballooned from 2.98 in 1972 to 6.80 (1973), then 6.10 (1974), for a record of only 5–16 in that span.