Deanna, who was a catcher for her high school softball team in the Santa Barbara area, would strap on the shin guards, chest protector and catcher's mask, and catch her son's fastballs throughout his youth.
Well, at least until Danny's fastballs started reaching the 89-90 mph range.
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"I think Danny was about a sophomore in high school," Deanna recalled, "and one of his fastballs skipped in and hit me, and I thought it broke my tibia.
"I still have a divot in that bone to this day."
That's when Danny shut it down.
"I had to because I was bruising her," Danny said. "But we still played catch and long toss. She's unbelievable."
Deanna served as her son's catcher through his youth. (Duffy family)
And Danny has never forgotten those special pitch-and-catch days with his mother.
"I wouldn't be here in the big leagues today if it wasn't for her," Danny said.
That's one of the reasons Mother's Day is so special for Danny. It's a chance to show her how much he cares.
This year, Danny is bringing Deanna to Kansas City for the weekend. On Sunday, Mother's Day, the Royals play the Orioles, though Danny isn't pitching that day.
"It's just going to be great having her here," Danny said. "I can take her out to dinner and just hang with her."
Deanna is proud to call Danny her son.
"It's just the perseverance he has shown," Deanna said. "He didn't give up when others thought he wouldn't make it.
Duffy strikes out Kipnis
CLE@KC: Duffy retires Kipnis in the 2nd inning
Danny Duffy strikes out Jason Kipnis for his first strikeout of the game in the top of the 2nd inning
"And now that he has made it, being in the Major Leagues hasn't changed him. He isn't lost in stardom. He still has that big heart, that big smile. He genuinely cares for everyone around him."
And that caring includes animals; Danny is an active supporter of KC Pet Projects. That love of animals started early.
"We had all kinds of animals in the house growing up," Deanna said. "Whatever he brought home to rescue. We had rabbits and cats and dogs. We had doves. He's always cared about any living thing."
Deanna also is proud that her son speaks his mind.
"If you don't want to hear the answer," she said, "don't ask him the question."
And what does Deanna expect from her son this Mother's Day?
"Nothing special," she said. "I just want to be there and get a hug."