The 22-year-old Norris said a growth was found on his thyroid soon after he was optioned from Toronto to Triple-A Buffalo at the beginning of May. After a series of tests, the growth was diagnosed as malignant.
"Meaning it contained the C word ... cancer," Norris wrote on Instagram. "Hearing this was alarming, yeah. Weird, yea, that too.
"I was given the option to shut my year down and get it removed immediately. However, seeing another doctor that determined I could wait until the end of the season reassured my gut feeling. Just Keep Playing."
The Blue Jays traded Norris to the Tigers as part of the David Price deal on July 30, one of the final moves Dave Dombrowski made as Detroit president/general manager. Al Avila, Dombrowski's assistant GM at the time, said in an email Monday that the Tigers knew about Norris' condition when the trade was made.
"This is a personal matter with Daniel," Avila said. "Yes, we did know about it before the trade. We expect him to have a full recovery and be with us in Spring Training."
Manager Brad Ausmus confirmed Monday night he was aware of the condition as well, and said he hopes everything goes well for Norris. Ausmus did not want to comment in detail on a personal issue, noting medical privacy.
Norris not only kept pitching, he pitched well with the Tigers. He became the first American League pitcher to hit a home run at Wrigley Field during an Interleague game against the Cubs in August, before going on the disabled list with an oblique strain. He returned to make four starts in September, including 10 scoreless innings over two starts against the White Sox.
Though the Tigers were out of postseason contention, Norris insisted he wanted to keep pitching, even through a 54-pitch first inning in his next-to-last start against the Rangers.
"Baseball kept me sane," Norris wrote on Instagram on Monday. "Regardless of results on the field, I forgot about it when I was between the lines. After all, I was just trying to get the heck out of AAA. And I did. I was revived with an opportunity, a blessing from God, with the Tigers back in the big leagues.
"Now that [the season is] over, it's time to get this thing out, so please keep me in your thoughts and prayers as I undergo surgery and come out 100% cancer free! As always -- #justkeeplivin"
Norris was originally drafted by the Blue Jays in the second round of the 2011 Draft out of Science Hill High School in Johnson City, Tenn. He made his Major League debut on Sept. 5, 2014, with Toronto. Many of his former teammates, who are in the midst of the AL Championship Series, had words of support for him before Game 3 against the Royals.
"He's one guy who doesn't dwell on negativity," said Blue Jays outfielder Dalton Pompey. "He's going to try to turn it around and make something positive out of it. He's going to continue to be himself, I know the fun-loving guy that he is and he loves life. And he's in tune with God as well, and I know he's going to be alright and get through this. He's going to be a great pitcher."
Blue Jays second baseman Ryan Goins added: "That's something that's bigger than baseball. When you hear something like that, you don't really care about the baseball anymore. You care more for the person. [Norris] is an awesome teammate, awesome person, awesome kid. He has a bright future in this game, but the main thing right now is just him being healthy."