"I'm feeling fine ... feeling better," Harlan Chamberlain said Tuesday, interrupting his lunch for a phone call.
He said his doctors told him he'd suffered respiratory failure from pneumonia caused by flu. Hospital spokeswoman Jo Miller declined to comment Tuesday, citing concerns about patient privacy.
Joba Chamberlain said his father left St. Elizabeth Regional Medical Center last Thursday, when the Yankees were in Chicago completing a series against the White Sox. He said his dad was in good spirits at home.
"He could be on his death bed and he'd have a smile on his face," the pitcher said at Yankee Stadium in New York before Tuesday night's game against Detroit.
Harlan Chamberlain said he talks with his son every day, reassuring him that he is recovering.
"I want to thank everybody for their thoughts and prayers," Harlan Chamberlain said.
Chamberlain was hospitalized on April 13 after collapsing at home. Joba Chamberlain talked to his sister after the Yankees' game against Boston that night and soon left for Nebraska to be near his father.
Joba Chamberlain rejoined the Yankees in Baltimore on April 19, after his father was taken off a respirator.
"You've got to be there for your dad," the reliever said. "All the times he's been there for you, you've got to be the one who picks him up."
Harlan Chamberlain had polio when he was 9 months old and uses a motorized scooter. He is deaf in one ear and can't fully use his left arm.
Harlan Chamberlain raised Joba as a single dad. Their father-son story of sports and family has been much told since Joba joined the Yankees last summer.
A starting pitcher for the University of Nebraska, Joba Chamberlain helped the Huskers reach the College World Series in 2005, where he beat Arizona State for the only CWS win in program history.
He was selected by the Yankees with the 41st pick in the 2006 amateur draft. He was called to the majors on Aug. 7 last year, and he has served as setup man for closer Mariano Rivera ever since.