(CNN)Baltimore Orioles star Trey Mancini announced in a post on The Player's Tribune that he has stage 3 colon cancer.
The 28-year-old outfielder and first baseman is likely to miss the 2020 season, or what's left of it -- the season has been delayed indefinitely due to the coronavirus pandemic -- to undergo treatment.
After having his annual physical and blood test conducted by team doctors, Mancini was told that his iron levels were low and that they needed to do another blood test.
Doctors thought that he may have celiac disease or a stomach ulcer, but it was much worse than that, according to Tuesday's post.
Mancini's father had stage 2 colon cancer in 2011 at the age of 58, and the athlete said it was "his last concern" and only a "remote possibility," as he was only 27 at the time.
"When I went in for an endoscopy and colonoscopy, the doctors told me that they were really expecting to confirm that I had celiac disease, which is found in your small intestine," Mancini wrote in The Player's Tribune.
"When the anesthesia put me under, I believed everything was going to be O.K. And then I woke up."
Mancini was diagnosed with cancer on March 6, and he had the tumor removed six days later.
On April 13, he began chemotherapy.
"Without the Orioles I never would have caught this before it may have been too late," Mancini wrote. "There was really no indication that anything was wrong other than me just feeling a little more tired than normal. Everything that comes up when you google colon cancer? I didn't have any of it. And so without that second blood test I probably would not have discovered the tumor until I had a total blockage of my colon."
Drafted by the Orioles in the eighth round of the 2013 MLB Draft, Mancini was coming off his best year in the majors with 106 runs, 175 hits, a .291 batting average and 35 home runs in 154 games.
"I want everybody to know that I'm O.K.," Mancini wrote in his personal essay.