MILWAUKEE -- Chicago Cubs right-hander Dan Haren went out on a high note Sunday, winning his final regular-season game, 3-1, over the Milwaukee Brewers before announcing he would retire after the team's postseason is over.

"That was it for me," Haren said after the game. "If I have to pitch in the postseason. I'll be ready for sure."

Haren, 35, isn't likely to make a postseason roster for the Cubs, though he finished strong, giving up just two earned runs over his final 17⅔ innings. He struggled, at first, after being acquired in a July 31 trade with the Miami Marlins.

Dan Haren won his 153rd career game Sunday, finishing 2015 at 11-9 with a 3.60 ERA. "If I don't pitch in the postseason, that's it," Haren said. Jeffrey Phelps/Getty Images

His ERA in August was 6.31, but it was just 2.36 in September.

"Happy the way the last few starts have gone," Haren said. "Being able to contribute to this amazing team. I'm just thankful to be a part of it."

Haren won his 153rd career game on Sunday as he completed his 13th year in the big leagues, producing a 3.60 ERA in his final season; he finished with an 11-9 record.

The Cubs play the Pittsburgh Pirates in a one game wild-card playoff on Wednesday with the winner moving on to face the St. Louis Cardinals in the division series.

"If I don't pitch in the postseason, that's it," Haren stated. "It's been fun. Hopefully there's a lot more games to go. ... If my name is called, I'll be ready."