Manager Mike Scioscia had considered a committee approach to the 162nd game but opted to let Haren go beyond his career norms in starts and innings pitched.
The start was Haren's 35th. After striking out Michael Young for the second out in the first on Sunday, he established a career high in innings, which he set last year while playing for the D-backs, with 229 1/3.
Scioscia said there would be no "artificial limits" set on Haren, who had been on a roll with a 3-0 record and 1.53 ERA in his past seven starts, striking out 45 hitters in 47 innings entering Sunday.
"I feel good and would like to have a nice finish," Haren said. "I was hoping I'd get the OK to go out there."
Heading into the final day, Haren was sixth in the Majors in innings pitched. If he goes six innings, he'll tie Chris Carpenter for fourth. Roy Halladay is the game's iron man with 250 2/3 innings, three outs more than Felix Hernandez delivered.
Jered Weaver, Haren's co-ace, is tied for sixth with Justin Verlander with 224 1/3 innings. It is a career high for Weaver, who said it meant more to him than his MLB-best 233 strikeouts -- one more than Hernandez and two more than Tim Lincecum. Weaver also had a career high in starts with 34.