The Oakland Athletics' 2005 season was their 37th in Oakland, California. It was also the 105th season in franchise history. The team finished second in the American League West with a record of 88-74.
The Athletics entered the 2005 season with low expectations. The team had won more than ninety games in each of the previous five seasons; despite this, there were concerns about the team's starting pitching. During the 2004–05 offseason, general manager Billy Beane traded two of the team's so-called "Big Three" starting pitchers. Beane traded two of the three, Tim Hudson and Mark Mulder, to the Atlanta Braves and St. Louis Cardinals (respectively); in both instances, he received prospects in return. The A's retained All-Star starter Barry Zito; despite this, many worried about the quality of the team's remaining starters. Some even picked the Athletics to finish last in the American League West, despite their having finished second (one game behind the Anaheim Angels) just months prior.
The A's seemed to validate these concerns in the early days of the 2005 season. On May 29, they were 17-32 (the third-worst record in baseball at the time); moreover, the team trailed the division-leading Angels by 12.5 games. The Athletics would follow this poor start with a stunning turnaround. From May 30 to August 13, Oakland would go a league-best 50-17. The surge was brought about, in large part, by the strong pitching of young starters Dan Haren (received in the Mulder trade), Rich Harden, and Joe Blanton. The team stunningly erased their 12.5 game deficit over this span. Oakland would pace the Angels well into September; at their peak, on August 30, the A's actually led the Angels by two games. In the end, though, the team fell short; a collapse in the second half of the 2005 season, combined with a dramatic Angels surge, saw the Athletics finish seven games out of first place.
The 2005 season also saw Athletics closer Huston Street win the American League Rookie of the Year Award. Street earned the honor after posting a 1.72 earned run average in his first major-league season; he did so while recording 23 saves. The Rookie of the Year Award was Oakland's second in as many years (and sixth overall).
|2005 Oakland Athletics|
|Major League affiliations|
|General manager(s)||Billy Beane|
FSN Bay Area
(Ray Fosse, Tim Roye, Hank Greenwald, Glen Kuiper)
(Bill King, Ken Korach)
(Fernando Arias, Julio Gonzalez)
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|Los Angeles Angels of Anaheim||95||67||0.586||—||49–32||46–35|
2005 American League Records
Sources:              
|2005 Oakland Athletics|
Note: G = Games played; AB = At Bats; H = Hits; Avg. = Batting Average; HR = Home Runs; RBI = Runs Batted In
|AAA||Sacramento River Cats||Pacific Coast League||Tony DeFrancesco|
|AA||Midland RockHounds||Texas League||Von Hayes|
|A||Stockton Ports||California League||Todd Steverson|
|A||Kane County Cougars||Midwest League||Dave Joppie|
|A-Short Season||Vancouver Canadians||Northwest League||Juan Navarrette|
|Rookie||AZL Athletics||Arizona League||Ruben Escalera|
LEAGUE CHAMPIONS: Midland
2005 MLB season by team
|AL West Division|
|AL Wild Card (3)|