Grant was diagnosed in December 2010 with chronic myelogenous leukemia, or CML, a rare form of cancer of the white blood cells. He recently wrote a letter to Mauer asking to meet and play video games with him. The Twins catcher responded with a letter of his own and invited him to Sunday's game, with the meeting set up by the Make-A-Wish Foundation.
"I just told him, 'Hey, let's do this,'" Mauer said. "'I want to meet you and try to figure out a good day to do it.'"
Grant and his parents, Stephanie and Rob, and his 7-year-old sister, Julia -- who live in White Bear Lake -- arrived at Target Field via limousine.
Stephanie said her son was "flabbergasted" by the experience.
"He was so excited with the letter [from Joe]," Stephanie said. "He would have been thrilled with just that. But then the limo came this morning and he just lit up. He kind of just buried his head, shy. He's humble -- just like Joe."
Using his own video-game likeness, Mauer was able to pull out a 4-2 Home Run Derby victory against Grant's choice of Justin Morneau. But that was only the beginning of their time together.
Mauer led Grant on a behind-the-scenes tour of the Twins' facilities, showing him the team's weight, equipment, and film rooms, and the indoor batting cage. Grant also saw Minnesota's clubhouse and visited with other Twins, including Morneau and Josh Willingham. But the trip to Mauer's locker highlighted the day, where he presented Grant with a signed bat and ball, as well as an armband and batting gloves. They also exchanged a signed version of each other's baseball card.
Grant is in remission but takes medication daily. The process can be a struggle, Stephanie said. He received a bone marrow transplant in December and visits a clinic four times a year, though Stephanie said her son has been doing well of late.
Stephanie called Sunday's experience "priceless."
But as much as Mauer made Grant's day, Grant may have put a bigger smile on the four-time All-Star's face.
"It's neat to be able to have that ability to put a smile on a kid's face or anything like that," Mauer said. "It's definitely flattering if they want to come and meet you and hang out. It's a lot of fun, too. It puts things in perspective.
"Grant's a great kid, he seems like he's happy-go-lucky. It was a fun morning, and I'm glad I was able to help him have a good day."