Dennis Eckersley made his debut in the American League with the Cleveland Indians on April 12, 1975 as a starting pitcher. In his first year he had a good start, reaching thirteen wins and seven defeats. In the election for rookie of the year he was defeated Fred Lynn of the Boston Red Sox. On 30 May 1977, he threw a no-hitter against the California Angels.
In 1978 he moved to the Boston Red Sox. This year, he had a record of twenty wins in eight defeats and an ERA of 2.99, the best record of his career. In 1979, he was still able to win seventeen games, but then he lost to class and consistency. After four average seasons, he was transferred to the Chicago Cubs. This he helped in 1984 for the first time since 1945 in the play-offs. Here the Cubs San Diego Padres subject, however, in the National League Championship Series. In the next two years he had to struggle with sporting and personal problems. He lost in baseball control of his fastball and showed only below-average performance. in the private sector he was struggling with alcohol problems. After the 1986 season, he went because of these problems in a rehabilitation clinic.
From the Cubs, he then moved on to the Oakland Athletics in his hometown. The manager of the A's Tony LaRussa was planning to use Eckersley as long Einwechselwerfer for the middle innings. After an injury of the regular Closers Jay Howell Eckersley took over his duties in the last innings and surprised and impressed with his performance in this position. After that he should no longer give this role in his time with the A's. From 1988 - 1990 he reached with his team in each World Series, but there was only one win in 1989 which rocked by the earthquake series against local rivals San Francisco Giants. His best year in the jersey of the Oakland Athletics had Eckersley 1992. He reached 51 saves and won both the Cy Young Award of the American League and the title of MVP. After Eckersley no pitcher was more honored with this award.
After his time in Oakland, he moved more to the St. Louis Cardinals. He ended his career on 26 September 1998 in the jersey of the Boston Red Sox. In 2004 he was elected to the Baseball Hall of Fame. Since 13 August 2005, his jersey number 43 is not longer available from the Athletics. Currently he is working as a television analyst for the Boston Red Sox.