"We are deeply saddened by the sudden passing of Bob Welch,” A's president Michael Crowley said in a statement. “He was a legendary pitcher who enjoyed many of his best seasons with the Oakland A's. He will always be a significant part of our franchise's history, and we mourn his loss. We send our greatest sympathies to his family and friends."
Welch pitched in the majors for 17 seasons, 10 with the Dodgers and seven with the A's. He was a two-time All-Star and won the 1990 Cy Young Award, when he went 27-6 with a 2.95 ERA in 238 innings of work.
"This is a sad day for the entire A's organization,” A's general manager Billy Beane said in a statement. “Those of us who knew Bob as a teammate and a friend will miss him greatly. My condolences go out to his family."
In his career, Welch was 211-146 with a 3.47 ERA and 1,969 strikeouts in 3,092 innings. He also amassed 61 complete games and 28 shutouts. He pitched in the playoffs eight different seasons, appearing in four different World Series. He won World Series rings with the 1981 Dodgers and 1989 A's.
Welch also served as pitching coach on the 2001 Arizona Diamondbacks team that won the World Series.
Welch is survived by his sons Dylan (25) and Riley (23), daughter Kelly (18) and former wife Mary Ellen, according to the A's press release.