Decker appeared in four games for Chicago in 1969, going 1-0 with an ERA of 2.92 over 12.1 innings pitched with one start, striking out 13 and walking six.
He’d go on to start 17 games for the Cubs in 1970, appearing in 24 games overall, going 2-7 with an ERA of 4.64 in 108.2 innings pitched, before dropping to a handful of games over the next two seasons before finding himself with the Minnesota Twins in 1973.
He’d have his two best seasons in the Majors in 1973 and specifically 1974 when he went 16-14 with an ERA 3.29 over 37 starts, with 158 strikeouts and a shutout over 248.2 innings of work.
Sadly for him arm troubles took over the next year, which saw him appear in only 10 games, going 1-3 with a bloated 8.54 ERA in only 26.1 innings pitched.
After another disappointing abbreviated season with the Twins the following year, he’d be out of the Big Leagues until a brief return in 1979 with the Seattle Mariners, where he posted a record of 0-1 in nine games, two of them starts, with an ERA of 4.28 over 27.1 innings.
For his career, he finished up at 36-44 with an ERA of 4.17 in 152 appearances and 710 innings on a Big League mound, with 377 strikeouts and four shutouts.