Duncan's wife, Elyse, is pregnant with twin boys.
"It's probably karma," Duncan said with a smile.
One thing is certain: It is a special time for Duncan and his family. Mother's Day is taking on a new meaning for Duncan, who is an outfielder for the Indians. The idea of soon becoming a father has given him plenty of time to further appreciate just how much his mom, Jeanine, assumed throughout his youth, and just how much his wife will be asked to take on as well.
Life in the big leagues can be hard on a family. Duncan understands this, because his dad, Dave Duncan, has spent parts of six decades in professional baseball as either a player or coach. A baseball mom often acts as a single mom during the season, and Jeanine Duncan handled that role with Shelley and his younger brother, Chris, with a blend of toughness and grace.
"She has like the full load on her," Duncan said. "She used to wake us up, make us breakfast, cook us dinner, take care of everything that was going on in our lives. You don't have someone there to pick up any slack for you. Dad's away for six months of the year and we only get to spend time with him for about three of those months. The rest of the time, mom's raising us.
"She had the duty of making sure we were on top of our schoolwork. She was enrolling us in Little League and taking us to practice, going to all our games. She was the loudest fan at every single one of our games, no matter what sport is was. Basketball. Baseball. Football. She was the loudest, most charismatic. Everybody loved that in her. She was like the ring leader of getting people together.
"She did an amazing job as a mother, pushing us and never letting us be complacent in any facet of life."
Shelley and Chris -- separated by two years -- did not make things easy on their mom, either.
"We caused a lot of trouble," Shelley said with a laugh. "We caused a lot of trouble at school and a lot of trouble in the neighborhood. But the best thing that I'll always remember is that, no matter what we did, our mom was always on our side. That's pretty special.
"I heard her yell at some people for us after we caused the trouble. She was always sticking up for us no matter what we did."
Duncan paused and grinned again.
"And then she'd yell at us behind the scenes."
Take, for instance, one of the times Shelley decided to stick up for his little brother. Chris, who is now a radio broadcaster in St. Louis after a five-year playing career with the Cardinals, was in elementary school at the time. Shelley knew there was an older boy who constantly picked on Chris during the bus ride home.
Shelley saw his opportunity when his middle school let out early one day. So, he rode his bike to their stop, waited until he saw the boy get off the bus, and then he beat the bully up.
"My mom's screaming, 'No, Shelley! No!'' Duncan said. "His mom comes yelling, 'No!' Chris hops on my [bike] pegs and we're high-fiving and saying, 'Yeah, we did it!' And we just zoom by mom and ride the bike home. So mom got stuck with it. She had to come home and she was angry. We explained why and everything. She always took our side."
Duncan is holding on to the rest of the stories.
"I'm saving all those stories for the book," he joked. "Me and my brother could sit here and go back and forth."
Duncan knows now how tough his mom had to be to deal with her two boys.
These days, though, he is in awe at a different kind of resilience Jeanine is showing. Duncan's mom underwent surgery for a brain tumor in August and has spent much of the last year going through extensive cancer treatment. Through it all, Jeanine has not lost her smile or her ambition, even making a trip to Arizona during Spring Training to see Shelley and his wife.
"She's getting better," Shelley said. "She's on a killer treatment program. They're throwing the gamut at her. They're swinging for the fences with this one and she's handled it pretty well. Sometimes she feels a little beat up, but she just takes it in stride. She's doing really well. She's been awesome.
"If you want someone to put a smile on your face, talk to her. She's good at that. She's always in good spirits."
Needless to say -- with twins on the way and his mom's health improving -- Mother's Day has taken on a new meaning for Duncan.
"A lot of times, Mother's Day sneaks up on you and flies by," he said. "I think when Mother's Day comes, it's going to feel a lot more special this year for a couple of reasons. More so than anything, just because of what my mom has meant."