The Phillies selected Ruthven in the first round of the 1973 draft out of California State University Fresno. He made his Major League debut on April 17, 1973 and went on to post a 6-9 record with a 4.21 ERA in 23 starts.
Ruthven logged 212 2/3 innings in 1974 and posted what proved to be a career-high 153 strikeouts. He spent time in the Phillies AAA affiliate in 1975 winning 10 with an ERA of 3.18 and went 2-2 with the Phillies with an ERA of 4.20 in 11 games.
On December 10, 1975, Ruthven was traded to the White Sox along with Roy Thomas and Alan Bannister for Jim Kaat and Mike Buskey. He returned to the Phillies in June 1978 in exchange for reliever Gene Garber.
Ruthven did not disappoint in his return to the Phillies, going 13-5 with a 2.99 ERA in 20 starts. The 1979 season was limited to 20 starts, but he still finished with a winning record of 7-5 despite a subpar ERA of 4.22.
A big part of the rotation for the 1980 World Series winning team, Ruthven went on to pitch for the Phillies through part of the 1983 season.
All told, Ruthven compiled a 37-34 record for the Phillies in the 1970s with an ERA of 3.87.